I am not sure what you mean by using Fleet of Foot, as that is a passive Feat.
This would break nearly all Actions that are intended to only be taken once per Turn, Sustain Persists being a major candidate here. Reintroducing a once per Turn limit for most types of Action would mitigate this, but throw the versatility you’re aiming for right out of the window.
Movement seems heavily punished, moving 20 feet and Attacking once already is the equivalent of a Focus Action, which usually lets you Charge, so move double your Speed and Attack at Disadvantage 1.
This also breaks most Feats that rely on certain Actions being restricted, like Superior Concentration. You’d need to rewrite all of those in addition to the entire Action system, not just Boon Focus and Multi-Attack Specialist.
In conclusion, I don’t think this is a workable system or even approach. I won’t stop you from trying, but as I am playing around with the concept myself I can tell you you need to think in far greater terms than just replacing Actions so they kind of fit into the same Turn.
What you would need to do is to rewrite half the system, that being the Action economy as a whole (what types of Actions can be taken at all) as well as every Bane, Boon and Feat that touch upon the Action system.