While my knowledge of In Nomine is limited to reading some source material a while ago, my Persona/Shin Megami Tensei knowledge is pretty thorough, so I have some comments.
The limitations on persona combat really depend on if you're looking at the P1/P2IS/P2EP continuity, or the P3/P4 continuity. In the former, personae and their effects can be used at any time. In the latter, some 'special condition' has to be true. In P3, that meant you had to be in the Dark Hour of the main game, or the Time Stop of The Answer. In P4, that means you have to be in the TV Land.
You might be better off if you try to release the investigators from their limitation - for all they know, they may not even *have* the limitation, they only *think* they do. Also, you might want to tie in the special effects of Teddy's glasses.
The older games were a lot more tightly related to the main SMT series - you had demons you could negotiate with, as opposed to mindless shadows. A thing you could consider is trying to reconcile P3/P4 to P1/P2IS/P2EP.
Consider checking out the LPArchive. They have LPs of the Persona games and a bunch of the SMT games, that could give you some ideas.
The limitations on persona combat really depend on if you're looking at the P1/P2IS/P2EP continuity, or the P3/P4 continuity. In the former, personae and their effects can be used at any time. In the latter, some 'special condition' has to be true. In P3, that meant you had to be in the Dark Hour of the main game, or the Time Stop of The Answer. In P4, that means you have to be in the TV Land.
You might be better off if you try to release the investigators from their limitation - for all they know, they may not even *have* the limitation, they only *think* they do. Also, you might want to tie in the special effects of Teddy's glasses.
The older games were a lot more tightly related to the main SMT series - you had demons you could negotiate with, as opposed to mindless shadows. A thing you could consider is trying to reconcile P3/P4 to P1/P2IS/P2EP.
Consider checking out the LPArchive. They have LPs of the Persona games and a bunch of the SMT games, that could give you some ideas.