Looks good - Your idea is quite a bit like TSR's DragonStrike from the sounds of it (which you can easily converted HeroQuest stats to and vice versa)
I strongly recommend having a read of the DragonStrike rules as I think it's exactly what you are looking for and should save you a lot of work
You can find a link to a PDF of all the DragonStrike rules in
This Post by Billiam Babble
I've written a very useful article on converting HeroQuest monsters to DragonStrike which you will find
Hereand although it's slightly less relevant I have a very long rant about Dragon Strike
Here
-----------------------------------
~The ravings of a single mad Goblin is bad enough, but such a power-hungry, malice-filled creature as Mortis can never hope to be understood~