Yeah, specially for a cast so large, it'd be way too complex. I could see that sort of thing working better in a more "regular" game where the party isn't as large.
When did you finished GC, again? Feels like it was long ago already. XD
My bias would say to go for it. Or maybe compromise. Pick up FoM and a different game and alternate? It's worth pointing out that FoM has two endings... though admittedly, I don't remember how different they are, but if you can still get two playthroughs out of it, you can do one now, and leave the other for much later, so you can move on to a non-mecha game or two before you pick up FoM or SRW again?
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Hmm, I wanted to use my Switch, but I currently can't. Well, maybe I can go back to Trails then...