Thanks.
As for the conversion, it's
techincally possible if(And i stress the IF part), you are willing to slightly alter both the cockpit,
and the figure to be piloting the craft.
The cockpit itself actually comes off(Like the ejection mechanism on the new Captain Scarlet White Falcons), and there are only three screws holding it together.
The problem, however, is that most of the newer Joes have what i like to call: "Dynasty shoulder pad syndrome", and their deltoid area is ridiculously bulky. There are parts of the FireBat cockpit that can be removed if needed, but the majority of work would be on the figure.
Here are some pics:

This was the only Joe i had to hand, and believe it or not, i had to remove one arm to get him to fit in there...
A figure with a less bulky set of shoulders would fit in a bit better, but it's still a squeeze...
And of course, you have to remove the seat, so a new one would have to be scratch-built too.
I would give this one a thumbs-down on the 1/18 scale-o-meter, because of the work involved(And even at the 1/24 it is originally, it looks like a small plane, so at 1/18, it's smaller than a light aircraft such as a cessna).
I removed the seat unit, and without it, there's room for a second pilot:

Remember that it doesn't look like this when you get it:

It looks like this:

Also, it has landing feet for some reason:

I felt that even a VTOL plane would need wheels for when it's on the ground, and unable to move under it's own power. Like during maintenance:

I don't know what they were thinking with that red canopy, but i also know it's not a problem to fix(I just vac-formed a new clear one, and dremeled out the old canopy, leaving just a frame to attach the new one to.
I honestly think it looks way better in clear.
I have a large stash of these things to make as variants when i get the time.
I hope that answered the question...(Even if it was long-winded...).
Bar.