Shooting epoxy over laquer will work, sort of. If you break through the epoxy while sanding, you may have lifting around the break through when you attemp to recoat it. The laquer will absorb solvents that the epoxy will not an a ring will occur.
Also, the laquer may crawl weeks after it is shot, if the solvents work their way through epoxy into the laquer. I had this occure weeks after the car was painted.
I have done it successfully but not without challenges along the way. If you can avoid it do. If you can not avoid it be sure to use the longest flash times possible and make sure you have good build with the epoxy.
Good luck,
John