Well Stimpy;
The cars, I am sure will have appeal to someone out there as everyone has their own tastes.

However, if I am reading this post right and you want to take the Fiero rebodies in a new direction, then I would suggest getting a side view of a Fiero and see where all your lines match up to a stock Fiero so you have a better idea of where all the break points will be to work around or modify on the Fiero. Besides the roof line which is an obvious one....
If you have a full on side shot of your ideas, post them and maybe someone on here can Photoshop them together with a Fiero and you can see where your points of contrention will be.
I think anything is possible, just a matter of how much work and what is left of the original Fiero. Look at the Lambos that pretty much only have the lower half of the tub and some of the front frame left by the time all the framing is put in.
God luck
don
Don,
Here is the original of the Mercury. I used a picture of my old 1986 GT. I lost the original pic and only have this one with Subaru wheels photoshopped on.

I used this pic off of eBay of an 88 Formula for the "58".

All the hard points are covered. The roofline is intact, the cowl is unchanged, the wheelbase, windows, all unaltered from factory. The roofline looks much lower due to the beltline running higher over the bottom of the side glass, just like like them Eye Tal Yan cars. What's left of the original Fiero is completely up to the builder, and that would be mechanical. Structurally there would be no need to change anything. The chrome bumpers would bolt to brackets mounted to the existing factory bumpers, which would remain intact.
I did think about this a little bit. I do have a Fiero.

It is the original Series 2 3800 Supercharged Fiero. Documented.