I could be wrong, but the hood of a car is pretty heavy. I think that the gas struts really just hold it open, the real power comes from the springs. Perhaps there is a spring you can either put under the door (on the inside), or alternatively a longer, but less powerful spring that goes over the top (on the outside). EIther way the locking mechanism would need to be firm.
But sounds like a good solution so far!
IF you get snow, would that be a problem getting it to open, especially if you were inside trying to get out. (assuming that there was an entry from the house, otherwise, the snow would have to be removed before you got in!)