[swaghauler]

Here's an alternate ACTIONS system that will allow multiple actions per round without much fuss. In this modified Mythras/Legend system, EVERYONE gets 3 ACTIONS. You would still roll [1D6 + Initiative Score] for INITIATIVE to determine the order everyone goes in (with appropriate reductions for wounds, suppression, etc...) BUT each person will now take 1 ACTION (of 3 total each). Each ACTION represents roughly 2 seconds of activity and can be movement, shooting, melee, etc... Once each player has taken their first (singular) ACTION from fastest (highest roll) to slowest (lowest roll), the first INITIATIVE PASS is over, 2 seconds have passed and the fastest Player/NPC now takes their SECOND ACTION. They are once again followed in order by the others until EVERYONE has resolved their SECOND ACTION; at which point the SECOND INITIATIVE PASS is over and 4 seconds have passed. The fastest combatant now starts the THIRD [and final] INITIATIVE PASS. Once the THIRD PASS is resolved, 6 seconds have elapsed and the ROUND IS OVER.
You can also have the number of ACTIONS reduced by suppression or wounds too. For example, you could give a loss of an ACTION for the Critically wounded threshold or being surprised. I like this system because it gives EVERYONE multiple options during a round. You can even rule that activities like reloading take multiple ACTIONS to perform.

Overall, I think this may give you the best balance between player/character "Agency" (multiple actions in a combat round) and the "framework and timescale" you need to successfully run an engaging adventure.