Hi Stephen,
Because WikiTree allows only one profile per person, that also means only one account per person.
Something you might consider is that there's a good chance at least part of your family is already on WikiTree. Some may even be managed by projects, which is a good thing. It means you won't need to add them again, and you probably won't need to manage them, necessarily. That might lessen the watchlist number.
You can also consider watching certain surnames on your tag list and seeing all the activity on those, without being an actual manager or trusted list member of those profiles. In order to keep my own watchlist down, I do that with more specific surnames like Glann and Kleinhampl. Those that are broader, I choose to manage so I can see just the family I am interested in, like Brown.
Unfortunately, there's no easy way around your situation. Another suggestion would be to manage just your direct line, and not entire sibling groups. You can still edit and improve those profiles, but leaving them open often encourages cousins who descend through those particular siblings to get involved and collaborate, including adopting the orphans.