Inspired by Maydole's Modal Third Way, as well as Gale and Pruss' Modal Cosmological Argument, I think there is promise in constructing a modalized version of the argument from motion - the Modal First Way (MFW). Let's start with three modal axioms:
A1. Everything in motion is possibly moved by another.
A2. The regress of movers is possibly finite.
A3. Whatever is contingent is possibly moved by another.
Motion, or change, is the transition of a potentiality to an actuality, as in the case of an acorn becoming an oak tree. Now, for a reductio ad absurdum:
P1. Assume that a First Mover does not possibly exist.
P2. If a First Mover does not possibly exist, then it is either necessarily the case that a) something in motion cannot be moved by another; or b) the regress of movers is infinite. (From 1, A1 and A2)
P3. It is not necessarily the case that (2a) or (2b). (From A1 and A2)
P4. Hence, it is possible that a First Mover exists. (From 1 - 3)
P5. Whatever is possible is either contingent or necessary. (Definition)
P6. Whatever is contingent is possibly moved by another. (From A3)
P7. A First Mover cannot be moved by another. (Premise)
P8. Therefore, a First Mover necessarily exists. (From 1 - 7)
Of course, one may imagine a possible world in which nothing is in motion. However, this wouldn't undermine our conclusion that a First Mover necessarily exists. For, without motion the First Mover would just exist a se and without any effect, much like George Washington would still be the same person had he not been the first president of the United States.
Let's sum up the argument in simpler terms:
1. Pure Act possibly exists. (Premise)
2. Whatever is possible is either contingent or necessary. (Definition)
3. Whatever is contingent is possibly actualized. (Premise)
4. Hence, Pure Act is necessary. (From 1 - 3)
5. Therefore, Pure Act exists. (From 4)
Then, in closing the gap between Pure Act and God:
6. Pure Act is either omnipotent or non-omnipotent. (Definition)
7. Whatever is non-omnipotent exemplifies the potentiality to grow in power. (Premise)
8. Pure Act does not exemplify any potentiality. (Definition)
9. Therefore, Pure Act is omnipotent. (From 6 - 8)