Personally, I would NOT allow reloads to be split into several rounds (or several phases). In my opinion, this is NOT a multi-round action. Allowing this split DOES increase the power of bows. jdale made some examples for RMU, there are plenty of similar examples for RMSS. For instance for short bow, starting with a loaded bow:
1) Normal: Fire, 60% - Deliberate: Load, 40%
2) Snap: Load, 10% - Normal: Fire, 60% - Deliberate: Load, 30%
3) Snap: Load, 20% - Normal: Fire, 60% - Deliberate: Load, 20%
4) Snap: Load, 30% - Normal: Fire, 60% - Deliberate: Load, 10%
5) Snap: Load, 40% - Normal or Deliberate: Fire, 60%
That's five turns of firing every round without any penalty. Similar situations occur for composite and long bow, of course. I prefer to impose a penalty for firing every round, and will thus NOT allow loading bows as multi-round (multi-phase) actions in RMSS. I've not yet tested RMU properly, so I can't say if I'd allow it in RMU or not.