Ok as the title says this is my personal opinion but i hope it points out one of the biggist gripes i have about marketplace content.
the issue i have is UPDATING, i like to keep the engine in its newest form so that i get all the new shinny stuff, this causes an issue if your project relies on MP content, as you can only install the content on a correct install version, to put it plain if you MP content hasn’t been updated for a few builds then your stuck, yes you can migrate to a newer build but you still have to have the older version of the engine installed just in case you need to replace the older mp content.
now just imagine you have MP content since the start of the Marketplace that hasn’t been updated and you decide you what to use it in a new project, how many versions of the engine do you want to dl/install or are you happy to migrate if you still have a project with the content in.
Thankfully UE4 is just a hobby so i can say sod it, and wasted my cash.
the option would be to allow the end user to re-validate the content for the current engine build