Altcoin support would be great given how high BTC transaction fees are now. I think it is reasonable to start accepting established alts, such as ETH and LTC.

The feature I'd most like to see added is an improved auto-betting system, similar to the one that used to be available on Dicenow. Dicenow's autobet system allowed users to roll up to 10,000 in rolls in one click, which included the normal auto-bet parameters such as increase on loss, max bet, etc. You could run 100k bets in around a minute, something I think many users would prefer doing than placing each bet one by one, which takes ages. I think this would be a great addition, and I haven't seen any other sites that offer it besides Dicenow.