This is probably a very specific thing that very few people have problems with BUT

I switched to my arena party, went to Ethernia, got into the arena, and entered a fight... only to remember that I've only fed my first stable recently and all of my arena pets (who are in a different stable) had fainted.

But it still let me enter the fight... and you can't use consumables in the arena, of course, so I lost the fight by default.

Could there be a warning that pops up if you try to enter the arena with a completely fainted party...? Like "Hey, none of your pets are alive right now. This is a bad idea. Stop." Just so that people like me who are dumb enough not to check if their pets are alive don't have to see their arena records suffer for our stupidity ^.^;;