Hi, thanks for the feedback!
The number of enemies you encounter per area goes up to 4 quite early in the game, so you end up having 4 to choose from. Reroll would be interesting, but there aren't enough mechanics to have a cost to it, nor was the game balanced around it, so it's probably too late to introduce it. I thought the area selection is enough of a substitute, giving you some control over what you'll encounter.
Area symbols are determined solely by the # of each type that can appear at all rarities, so I agree that it can be a bit misleading early game. Fire and Electric combined have only 3 mons at common level, so there have to be some wildcards to fill up the quota. Not sure if I can fix this. I guess I can only recommend looking at the full list of possible mons and use the type icons as a very general guess
Not sure what you mean by team-wide penalty for assembling a comp - there are actually party buffs for having multiples of the same type.
From my experience, the Steel bonus is more relevant late in the game, when battles take longer. It's really bad early when everything dies in 4-5 hits
Thanks for playing!