All I'll say is, there's going to need to be a line drawn somewhere, and I don't envy the job of deciding where it goes.
People running teams composed only of players from their favorite real-life team aren't putting their "best" team on the field, but they're having way more fun, and if that weren't allowed, it'd be a loss large enough to render PT somewhat inaccessible and pointless to many.
This strategy, one team, in isolation, seems fine. If it's maximizing your enjoyment of the mode, I see no issue.
I also see the issue if a significant percentage of teams in a division/league are doing this (and it may only take 1-2 to significantly affect PP payout for that league).
I'd considered making an "all-pitcher" team (or as close as one could get) where basically everyone is a two-way player and they just trade off who starts (like many kids leagues in real life). It'd probably be pretty bad, because outside of Ohtani and some historical guys, you'd have to roster guys like...Matt Davidson? Chris Gimenez to catch? That team would be
trying to win, but it'd be bad at it.
I'd also like to thank the OP for a reasonable and constructive introduction to the topic.
EDIT: And a line has been drawn already. Easy enough!