[kh99]

In general, you could take the code for a given task from admincp/misc.php and make it a plugin using hook cron_script_cleanup_daily (to run once per day). But it would take some work because of course those maintenance tasks are written for an admin to do from the admincp, so some of them only do a certain number of records per run (and then show some kind of "continue" page). So the mod you suggest would take some work.

I should also mention that I don't think there's anything in the maintenance menu that should have to be run regularly, which is probably why it's there and not in a scheduled task already.