Motors can usually be revived and even if you need a new one and relocate to the boot its going to be a faction of the cost of buying a hardtop, plus if you solve the problem with a hardtop you aint gonna be enjoying the spring / summer top down - seems a drastic solution.
Once the motor is relocated (there are several members who can do this with out removing the roof at very reasonable cost) then theres no need to have a hardtop if the only reason is to protect the motor :?