Is a combination of sheet EPS and closed cell foam between rafters feasible as a combination?
If you spray by yourself, you might run into problems. Check out you tube for horror stories using incorrectly sprayed on foam.

Next. You could place 3 1/2" unfaced insulation between the rafters. Use thin wire and tiny nails nailed to the bottom the rafters to hold the insulation in place like a zig zag pattern. Then add 4" closed density foam to the rafters using long screws with washers.

When you said rafters I hope you were talking about the part that is connected to the roof.

If you were talking about the wood that the ceiling below is connected to, those are called ceiling joists and that is a whole different procedure.

Also, you didn't say trusses, which is another different procedure.

You could add a ridge vent and soffit vents.
This would give you a pressurized vented attic.
See youtube.com for more info.