You could count on my support to run a witness node, or even host a webwallet and faucet. In fact if one of the current bridges is not interested in supporting the new chain, then I would be more than willing to work to develop a bridge between other crypto and this new chain. I could not touch fiat unfortunately.
I still have concerns, but I think it would be a really great experiment, and if my concerns are unfounded then it would be a superior implementation than the current system.
I think I have found a better way to express my concern as well. In the current system bitUSD is a derivative that is backed by at least $1.75 worth of BTS. Since this BTS can currently be sold, anyone wishing to exit bitshares can sell BTS directly. Thus someone who is long bitUSD, that wants to exit bitshares will sell their bitUSD for BTS and convert their BTS to whatever other currency they wish. There are two distinct markets. We have a derivative tied to USD and a backing asset that is not tied to USD.
Under this proposal bitUSD would still be a derivative that is backed by at least $1.75 worth of BTS. However because BTS can not be traded for actual other currencies, in effect the backing asset would be the externally trading asset. We would end up with a derivative that is backed by itself. I cannot view such a system as stable.