It’s definitely worth considering!
I think this definitely points to “figuring out a good incentives mechanism” part of the design.There is an interesting dynamic at play here, between rewarding IL committee members for including all transactions they see (e.g., getting more rewards if they include a transaction no one else included) and rewarding the block producer based on evaluating the difference between transactions in its IL aggregate and those in local ILs. Happy to discuss this further, I think we mentioned it in the post and to me, the incentives part definitely seems to require more research. I remember @Julian had thoughts about something very close to what you’re describing for the Eval function too.
About ring signatures/plausible deniability, this is a parallel, very interesting research topic we’re working on. I recommend checking out our anon-IL design in which we specifically use ring signatures. But this needs a lot more research, and my personal opinion is that it’s quite unlikely we’ll have an efficient/robust mechanism for this in the short-term.