If you have a lot of sites, why don’t you use a virtual private server? Then you have root access and can do whatever you want. You can rent a VPS for about €50 to €60 per year, so if you have a lot of sites, this could cost less than shared hosting. Several companies offer this, obviously I can’t recommend one here, but if you google for virtual private server you’ll find one that meets your needs.
The downside is that you have to administer your server yourself. If you’re already comfortable with administering a Linux machine that’s no problem but otherwise you’d have a lot of learning to do.