So, after some more playing, it turns out that the game I was testing the 16-bit interpreter with, the Vault of Hugo, won't restart even if you only use the standard library (also, a small Roodylib game will still restart in the 16-bit interpreter). If I drop the HugoFix debugging suite and identical and plural object support from Vault of Hugo, the game will work, but add either one of those and it's back to shenanigans. I take this to mean that the issue is deeper than anything I can do to fix.
For the most part, not being able to provide games for the 16-bit interpreters isn't a big loss. It'd really only be useful for things like the @ party thing mentioned in the last post (although it's still very possible that IF doesn't even need to meet the 1992 requirement) or targeting other real die-hard retro fans.
When I do the @ party thing, I'd like to go somewhat hardcore. I think that means that I'll probably have to use ZIL for that, which is cool, but my only regret is that it's probably too late this year for me to write a ZIL game in time for @ party. Still, next year, the @ party might be a great thing for a ZIL competition to piggyback on to.