Here is reality!
If you want a convertible, buy a convertible!
A cut up hardtop made into a psuedo-convertible becomes a nothing. A nice hardtop is a worthy desirable car, a nice convertible is a worthy desirable car. The alternative you propose is going to accomplish the destruction of a hardtop, period. You will sink your money, time, and heart into a pit that probably won't ever see the light of day.
I'm sorry to be so pessimistic, but truth is truth.
Find a convertible and love it!
Best of luck!
I love technology.