This sounds pretty legit, i can offer a couple of tips or two as i am an avid gamer, and i'm also helping one of my friends develop something as well.
1. How are you planning to do the layout of the game? Is it gonna be a top down rts style, or more of a 3rd person mmo sorta feel.
2. Did you ever think about trying something new with the concept. Like having a "PermaDeath" feature, something like "Realm of the Mad God", or "Day Z". It's just an idea, but you can run with it. You can set it up in a way, that your coins won't be affected by your death, but it does make the pace overall faster if your looking to go on that approach.
3. I see you put "Receive a coin when you kill a player (this is taken from the cost of the “dead” character.. e.g. 1 coin)". You can make it so that you get a coin taken away from you if you kill a player that is "off limits" (ex. have been killed to frequently). It would help new players who just start out to actually have fun with the game, instead of having that snowball effect where more experienced players are farming them for coin, xD.
4. "Characters can make one action per block. For example, move one square and/or cast an ability (or speak)". I didn't understand what you meant by this (sorry for my idiocy,
). I'm not to sure if it has something to do with blocks dealing with BTC, or that there is literally "blocks" that there going to be moving on, something like final fantasy tactics.
5. I love your ideas on the classes (i'm a sucker for diversity
) If you can, Try adding more classes.
(i would add more, but i dont want to bore you with so much reading, xD)
Also if you need help with anything dude, I'm more of a gamer than i am a BTC guru. So if you need help or need some new ideas. Feel free to contact me whenever, I always love seeing people try new things. And since BTC is pretty dam new, the potential is unlimited (depending on how much work your trying to put in)