I may be fooling myself, but I have experimented with that a little bit (mainly to get a higher ROF for fire-and-forget missiles), and it turns out that you can get a fire-on-move opportunity at very low speeds (i.e. not from a complete halt, but not 30kph either) with a missile weapon size of 1 or 0 and a very high vehicle ROF (say 20).
This works (sometimes) for dedicated ATGM launchers. I have no idea if it would be worth anything if the missile isn't the main weapon.
Besides, giving a huge ROF value to a tank might have some undesired side effects re. cannon shots and so on...
Anyway I'd say that the experience rating plays a large role therein too.