Regarding the questions about the ETH bankroll.
You as a user cannot place a bet, unless there is a bankroll in the selected currency (This case ETH).
So until we grow the ETH bankroll, users cannot place bets for that currency.
So dont you think that it better if you disable the option to deposit ETH till you have enough bankroll to accept ETH bets?
Players may feel something bad if they are able to deposit ETH but they cant place any bets with it.
The same as your free balance giveaway, it is better if you give btc only as it is useless if you give ETH but players are unable to use it.