Shutting down investments was stupid as hell. The only benefit to using your site if there is a variable edge is if the bankroll is enough to which you can bet up to / to win 20 BTC per roll and have an edge of 1% or less. The current leader is PrimeDice which offers 1% house edge fixed and offers ability to win up to 20 BTC per roll. Thus, the variable edge doesn't matter with your site unless you build a big enough bankroll because anyone who wants to bet a lot is simply going to go a more trusted site that offers higher payouts.
Dumb, dumb, dumb move on your part.
Agree with you that a high enough bankroll is needed to make the variable edge system work. Otherwise, the site will only be used by small bettors.
The 20 BTC limit in PD is about the payout of a bet but not about profit. So if you play 2x bet, you can only wager at most 10 btc each time; and if you play 10x bet, you can only wager at most 2 btc each time.