I hope I wasn't sounding skeptical... I know I've seen one or two vehicles out there (pictures at least) where the guard was a "flip up" design. If you're attaching to the hood directly, I suppose that would solve the attachment point issue However, it is placing more stress on the hood latch. I've had a hood come up on me before and it's not a pleasant experience.
I suppose you could come up with a hook type mounting system that would work out alright. Similar to the roof racks style maybe? Something that would work with a gutterless mount? Since it is right up fron, it's going to catch a lot of wind and your mileage will suffer. A very secure latch will need to be in place to keep it from flying back on yuo as well. Remember, you may be going down the road at 65 mph, but if you have 30 mph headwinds, your combined wind speed just jumped to 95 mph. Consider bow waves from semi's going down the road too.
That's probably why I like the overhead flip over design better. In stow away position, it's already out of the main slipstream having less of an effect on normal driving.
Again, just my thoughts. I'm certainly no engineer. I do have a weather station modified for mobile use on my truck as well so I have come a cropper of the various issues. Mine sits on a telescoping mast attached to the rear of the camper shell. It has 2 braces and a third base attach point. I'm no longer worried about the mast flying off. It's been in 100+ mph winds and survived rather well. I am worried about metal fatigue though as it's mounted permenantly.