Just go with alt accounts. In my clan we have some alts incase we don't meet upkeep and it has always worked so far. That way you also don't need to recruit people you don't want in the clan.
Everything seems to go in cycles in Runescape (to everything... there is a season). Our clan is more active now and we're having fun doing various activities together. That's the most important thing.
We do have several members who enjoy playing iron accounts in addition to their regular membership account. They step in to help as needed to make sure upkeep is paid each week and will happily join in if we set dates to finish our upgrade.
As suggested, we'll revisit citadel goals when the Invention hype dies down a bit. More than likely, we'll also ask friends of the clan if they'd come help us with the final push to finish building by joining our clan temporarily (if not longer).
No matter what, I'm digging my heels in and won't pressure anyone about capping anymore. It simply causes more stress for everyone than it's worth.
AND I'll continue hoping that one day in the future some J Mods will see the wisdom in doing what is necessary to get rid of the visitor count requirement.