Some great info!
Voting
I agree on the fact that there is a distinction between voting and “actual participation”. I think voting, and the participation there, regardless of how little it may be, should be incentivized. This is to encourage high voter participation!
The more active votes there are, the more difficult it becomes for any one entity to amass enough control to exert their own influence over the DAO as a whole. Voting may not require much effort, but this does not mean that it is not important! Thus, it should be incentivized to not only hold ENS, but to ensure that it is being assigned to ACTIVE delegates. *Active delegates being important here, because assigned to an inactive delegate ultimately renders those votes useless.
Actual Participation
The other topic you touched upon is “Actual Participation”. Personally, I prefer the term “compensation” when referring to encouraging “Actual Participation”. I prefer that because it more properly defines that one who is activiely participating is spending their own time and resources to help the DAO, and thus are not simply being incentivized to do so, but are actually being compensated for their time.
I like to think of a DAO as a self-run company. No company would attempt to incentivize unpaid workers to perform work in the hopes of receiving an incentive down the road. They, instead, compensate the workers with a salary or pay for their time.
Thoughts
Both of the above actions are a necessity for the DAO to succeed, but each likely require a unique strategy to ultimately find a successful solution. Further, quantifying actual participation is likely going to be very complex and nuanced as you mentioned, thus I suggest starting very simple to get the ball rolling and allowing the DAO to audit and adjust as needed - or even ultimately scrap the phase 1 incentives with a long term elegant solution.
On that side, you have some great ideas such as bounties and POAPs. I LOVE POAP. I wrote an article highlighting POAP and the capabilities they bring to web3, the possibilities they open up, and how useful they may be in the future. POAP is a useful tool that ENS should leverage. POAPs for joining twitter spaces, discord calls, etc will be very useful. HOWEVER, there is one caveat…they have to be carefully delivered. We would need to ensure that POAPs are indeed being delivered to those who are participating, while also ensuring they are not being delivered to farmers. Easy to do if manual (well, manual is not easy, you know what I mean), tougher if attempting to automate.
My main goal would be to get a simple incentive started sooner than later. Perhaps one solution would be to set incentives with a 3 months lifetime, such that a proposal would need to be created in 3 months to either continue the incentives or propose a modified incentive plan based on successes and failures of the prior generation of incentives.