OK, first of all LCD Top Guns don't have recoil, they "vibrate" not even close to the same! also i have NEVER seen anyone successfully hack a light gun into another case, i have seen people try, never seen it successfully.
OK, next problem, i didn't think Time Crisis played at full speed on MAME, i haven't tried in a while so i may be mistaken. your best bet might be with a PS2.
if you do go with a PS2 and pick up a few Guncon2s you can also use them in Mame. guncon2pc drivers have got quite good, if you dint mind ALOT of tweaking to get them just right it could work for you, plus they look "right" and have GREAT recoil. i have 2 and wouldn't change except to LCD top guns (i never use the recoil, i find it too annoying/loud/distracting)