Disclosure: I work at Shippable. I think the latest features we launched at Shippable meets all of your requirements. You can mix and match on-demand and dedic

Disclosure: I work at Shippable. I think the latest features we launched at Shippable meets all of your requirements. You can mix and match on-demand and dedicated nodes, allocate them to specific projects if you'd like, all of this is available in our SaaS edition, and pricing is (in my opinion) quite reasonable.