The obvious response is that I should just pick the most promising one and focus on that, and put the others to one side.
Reasons not to do that are:
(1) all are quite important (addressing significant problems for important industries or consumer groups), but for different reasons,
(2) I actually enjoy the working on different things - each has appeal for different reasons,
(3) I'm an older founder with a family/mortgage, and see it as more prudent to spread my risk across a few different bets than go all in on one (which I've done before when I was younger), and
(4) though the concepts are quite different in terms of industry/product functionality/technologies required, I can see some commonalities in the types of people that would be interested in working on these ideas (for the same reason that I like working on all of them), but also some differences in the fun-vs-importance/impact of each, and I feel like there's some advantage in being able to rotate team members from one project to another every few months, spending some time on the more fun things, and then some time on the more "important" projects - or whatever they prefer.
But I'm still wrestling with the pros and cons of going this way vs just focusing on one thing. I'd be happy to hear thoughts from people as to whether this kind of thing could work, and what pros/cons I might not have considered.
[1] Several years ago I worked as an employee for an agency/studio that did "we'll build your startup for you" kind of work (not for equity, just cash); we had some solid wins, but for the ones whose startups didn't work out it was hard to see all that money (usually founder savings) go to waste, and I would never want to do that again.