Mixed language decks

My buddy has serious concerns about this. Have yall run into this at yalls locals or anything? Do we see this being a long term situation, or just like a temporary band-aid fix for supply issues? Has it caused anybody issues in their games?

Edit: his concern being i guess having to trust that the other player knows the effect of their card or isn't fibbing, or having to call a judge everytime he doesn't know what the card is