I think you may have a first there - perhaps a bit overkill but it would be nice since a lot of times I have a fairly heavy "Mag's Bag" on top of my trunk. Being able to control the heft with a gas spring when opening the case would be nice. As is, I've got to carefully let it extend on the "leash" stops so as not to overstress it.
If you decide to go ahead with the project document it here for everyone to see. Details and pictures are NICE.
Heck, you may even get included in the Ghetto Hall of Shame!
Just remember, in order to qualify:
1. It's got to be functional
2. It's got to be very inexpensive
3. It's got to look good and feelgood
4. It's got to be easy to implement
5. It's got to look OEM, or darned close
6. It's got to be something that can be built with everyday hardware available at ACE or Home Depot