monsterer, xeroc, are you saying we can't do this yet, or that the ideal way of doing it (ACCT) is not available yet? To get commercial product to market, there are always trade-offs to be made. A company can go broke waiting to achieve the ideal.
There is no trust free way of doing this currently. If you don't mind that compromise and if you could use a backing of bitBTC instead of BTS for other bitAssets, then you could simply use both metaexchange / blocktrades for redemption.
monsterer, could you explain the mechanics here a bit further, as it could be the simplest starting point as a stepping stone to a more distributed trust system. My understanding is that a gateway only retains enough inventory to facilitate transactions. In this case, a potentially large backing reserve would need to be held for all the bitBTC issued. So for example:
User sends real BTC to pool in return for a new bitBTC, real BTC retained in reserve
User sends bitBTC to pool to be destroyed, for a real BTC sent back from the reserve
The key would be to have strong controls on the integrity of the reserve.