It sounds like you are describing something like a hosted Nextcloud [1] instance but I have no idea if that makes sense cost-wise. They have a comparison page

It sounds like you are describing something like a hosted Nextcloud [1] instance but I have no idea if that makes sense cost-wise. They have a comparison page [2] that also mentions some of the other related services. I have only used the self-hosted version of their applications and honestly have no idea how much their hosted solution costs. [1] - https://nextcloud.com/ https://nextcloud.com/ [2] - https://nextcloud.com/compare/ https://nextcloud.com/compare/