Here's an option to reduce the risk of a single entity controlling all of XBTC causing systemic risk. How about I transfer XBTC to the developers and they by enrolment allocate portions of the XBTC to entities who wish to underwrite the value of XBTC to BTC. The more the better. That way, if any single entitty was to do a 'runner' it would have a reduced impact to the value of XBTC.
In such case, we need 100+ underwriters, I think.
To be honest, I wouldn't be so inclined to this mechanism. It would incur overhead of the developers and they haven't agreed to any such role. They remain the neutral by writing the protocol and not the handling of a particular asset.
The greatest disadvantage I see so far is that there is a large risk of the underwriter.
Let's be clear that XBTC would merely be just like any other asset issued on Counterparty and is not trustless. It's not designed to be a replacement for btcpay. It is just another choice in the way in which people can use Counterparty.
I think if Poloniex or another exchange were to provide such a service it may help move greater volumes on the DEX.