Thanks for this indepth post! Very curious about the town upgrade costs. 200 gold could just be the start, I imagine more costly upgrades especially in expansion style content. I don't mind the gold cost to upgrade the town as long as it seems fair, you are able to earn gold in the mode, and you are rewarded for spending the gold.
I see the p2w aspect of this mode similar to Standard Hearthstone... If you play every day, and you're dedicated, you'll have no issue being f2p. You'll be able to earn the best cards/mercs, but don't expect *every single card/Merc* in your collection... That's an unrealistic goal.
You made a great point though, that this game mode is heavily reliant on pve. So it really doesn't matter what power level you are. I think part of the fun is starting from nothing and growing your team. That's what makes RPGs fun!