I like the idea of allowing melee attacks as simple actions; hell, even spells can be reckless cast. I'd probably allow the same for Sprinting, too, but keep the max 1 attack action per combat turn, regardless of source bit.
Personally, the idea that if I have to sprint to reach my target I can no longer attack if I charge them is somewhat ludicrous. The current rules can end up producing weird results like a character sprinting to charge his target in one round, only to have the target move just 2m away so the character has to make another sprint test, precluding an attack action.