Gurren Lagann is the Epic mecha anime of this time in history. No filler. Suprize plot twists that make sense. awesome battles.. Developed side charicters.
The ending was the ending it needed. Gurren Lagann is everything a series should be. They actually added an extra episode rather than follow standard
length. The end battle is something that can actually produce crossovers without needing plot devices.
Eva Angels have a specific format that makes them different from most Kaiju swarms. First is that they learn from their mistakes collectively. When you kill
one... the others upgrade to compensate for how you killed the last one... and don't forget previous lessons. Sachiel is a pretty standard Kaiju with good
wepons. But failed becuase you could grapple it. The 4th used energy limbs so you couldn't grapple it and not get shredded. Ramiel decided this whole
melee thing wasn't working and turtle with a main gun. Ramiel's failure was its inability to dodge. The angels tried nuking them from orbit...
Sabatoge, extreme enviromental conditions and a decoy... Every Angel tried some thing different. Everyone was a different challenge. I could go through the
list, but I think that much is clear.
The reason that kind of enemy is a terrible idea to fight in swarms is it upgrades the next batch for everyone you kill. So by the third swarm you'd be
forced to swarm yourself invent new super weapons largely different attack methods with each battle. The planet would get slagged if the main characters held
out for any length of time at that level.
First this is technically a fusion, so not a crossover, but that is a weasel smack down method. Pointing out its not a crossover. Why I said its a poorly
'executed' (quotes as it theoritical) is that it fails, not becuase of the inherently conflicting storylines (that I know of). Not because the series
couldn't (nessessarily) go together... not because of it just being a mind meltingly, bad idea (see previously suggested lemon)... it is poorly executed.
Meaning the idea fails from the way it is done... not because the series would (nessassarily) mesh badly. It is the way you suggested they combine. The angel
dropped in basically whole sale (even if they are shrunk down).... the Eva not existant really.
It is easy to combine the things. 3 pilots of the Eva's could end up as the 3 pilots a decade later. Tokyo 3 could end up as the base for the Getter Robo
and the Evas (post episode 23) as the disturbingly powerful home defense. Hell, Give Shinji his S2 (or all the Evas them) and the Getter Enimies are sqished,
diced and mangled. Considering the mecha in Getter are listed as around 38 meters tall... and using the height I found in one of the Eva manga (300 meters)
size wise there is no comparison...
Hell a crossover formatt where the Getter team is based in Tokyo 3 and both an Angel and the enemies that attack in Getter series attack at once and tear each
other to pieces could be hilarious. Give Sachiel a bit of the spotlight. Have the Getter fodder enemies as the expendables (instead of the UN) during the
first episode (both enemies have terriblely linked attack scheduals). Have Getter be there instead of Jet Alone... both series can run at roughly the same
time... the Getter is near useless vs. Angels but just what they needed for the Dinosuar Empire.
You could also do a crossover where the The Getter Team runs into a big nasty they can't kill... so they lure it to Tokyo 3 where the Evas are unmothballed
and the pilots of the Evas have to come back into the field to deal with the Uber mech. Make it post episode 23, no movies or the last 2 episodes, and you can
do a 10-20 years later thing... where the Dinosaur Empire or whatever just didn't see the Eva and Angel war.... they decided they could take the humans
after the ice continent blew up.
The crossover itself can be done... probably well... its the specifics of your set up and the idea of fighting billions of Eva Angels that fails. Hence: Good
idea... bad execution.
The ending was the ending it needed. Gurren Lagann is everything a series should be. They actually added an extra episode rather than follow standard
length. The end battle is something that can actually produce crossovers without needing plot devices.
Eva Angels have a specific format that makes them different from most Kaiju swarms. First is that they learn from their mistakes collectively. When you kill
one... the others upgrade to compensate for how you killed the last one... and don't forget previous lessons. Sachiel is a pretty standard Kaiju with good
wepons. But failed becuase you could grapple it. The 4th used energy limbs so you couldn't grapple it and not get shredded. Ramiel decided this whole
melee thing wasn't working and turtle with a main gun. Ramiel's failure was its inability to dodge. The angels tried nuking them from orbit...
Sabatoge, extreme enviromental conditions and a decoy... Every Angel tried some thing different. Everyone was a different challenge. I could go through the
list, but I think that much is clear.
The reason that kind of enemy is a terrible idea to fight in swarms is it upgrades the next batch for everyone you kill. So by the third swarm you'd be
forced to swarm yourself invent new super weapons largely different attack methods with each battle. The planet would get slagged if the main characters held
out for any length of time at that level.
First this is technically a fusion, so not a crossover, but that is a weasel smack down method. Pointing out its not a crossover. Why I said its a poorly
'executed' (quotes as it theoritical) is that it fails, not becuase of the inherently conflicting storylines (that I know of). Not because the series
couldn't (nessessarily) go together... not because of it just being a mind meltingly, bad idea (see previously suggested lemon)... it is poorly executed.
Meaning the idea fails from the way it is done... not because the series would (nessassarily) mesh badly. It is the way you suggested they combine. The angel
dropped in basically whole sale (even if they are shrunk down).... the Eva not existant really.
It is easy to combine the things. 3 pilots of the Eva's could end up as the 3 pilots a decade later. Tokyo 3 could end up as the base for the Getter Robo
and the Evas (post episode 23) as the disturbingly powerful home defense. Hell, Give Shinji his S2 (or all the Evas them) and the Getter Enimies are sqished,
diced and mangled. Considering the mecha in Getter are listed as around 38 meters tall... and using the height I found in one of the Eva manga (300 meters)
size wise there is no comparison...
Hell a crossover formatt where the Getter team is based in Tokyo 3 and both an Angel and the enemies that attack in Getter series attack at once and tear each
other to pieces could be hilarious. Give Sachiel a bit of the spotlight. Have the Getter fodder enemies as the expendables (instead of the UN) during the
first episode (both enemies have terriblely linked attack scheduals). Have Getter be there instead of Jet Alone... both series can run at roughly the same
time... the Getter is near useless vs. Angels but just what they needed for the Dinosuar Empire.
You could also do a crossover where the The Getter Team runs into a big nasty they can't kill... so they lure it to Tokyo 3 where the Evas are unmothballed
and the pilots of the Evas have to come back into the field to deal with the Uber mech. Make it post episode 23, no movies or the last 2 episodes, and you can
do a 10-20 years later thing... where the Dinosaur Empire or whatever just didn't see the Eva and Angel war.... they decided they could take the humans
after the ice continent blew up.
The crossover itself can be done... probably well... its the specifics of your set up and the idea of fighting billions of Eva Angels that fails. Hence: Good
idea... bad execution.