From what I've seen a lot of owners just want to get playing with their teams. Whether it be going public for one season to fill, or merging and losing all of their history, they're for it as long as they can get playing. If the alternative is sitting for months or losing all history, I think a lot of worlds would roll with a few SIMs for one season than do that. Of course, there would be some who wouldn't consider playing with SIMs, just as there are some that are strongly against going public or merging, the current options available now, but it is a fit for some worlds.
Ensuring that SIM doesn't completely ruin a team for future human owners would be key. And I don't think it should be immediately available, only a remedy for periods of slow demand, I think 45 days is a solid number.