Semi-transparent menus would be difficult to implement, and be a bad idea besides (visibility issue). The menu is not laid over the field screen, but an entirely different engine module. Crafting a driver to do the work of creating backgrounds is already a significant issue, and would likely instead be solved by (difficult) executable editing. But adding in a 'on the spot' screenshot generator, with alpha processing? That's just beyond the scope of what's reasonably doable.
Give it up. It's a complete non-starter.