As I've said, I'm sure it'd be vastly easier to use Top-Heavy than Lionizer; if you want to recreate a
bison, a
rhino has much closer proportions than a
cat. In addition, I'm not sure you'd be able to easily add the horns without obstructing his transformation; you'd probably have to carve out a small section inside his torso to allow for them.
As far as mounting them as a tank cannon, it may be possible, but I don't think it's the legs that would pose the problem, as they can be easily posed out of the way. Your issue would be with the tail, which acts as the trigger to transform to gun mode, and in either case sticks out of the back.
You'd probably be far better off coming up with a different solution for the cannon barrel and mounting the partner as an extra 'sidearm' on the top.
And this here is why you really don't need to go through all the hassle of trying to turn a falcon (Sights) into a bat...
http://www.tfu.info/1990/Decepticon/Sou ... ndwave.htmAs for the combiner, do you have any hints on how you intend to make it work? And do you intend to make it a seven-part combiner or a six-part combiner with seven members? Remember there were only ever six members at any one time; someone (was it Gaihawk or Hellbat?) was drafted in after Deathcobra was killed.