so, take all 4 Insistences right off the bat. that will give you
- humility - +1 for attack with a push
- advantage - +1 for disarm or damaging equipment
- subtlety - +1 for a back attack
- time - +1 for shifting position in initiative order
then take aggressive assault (the push), disarming parry (disarm), lunging attack (move behind), and roll into position (shift initiative). that gets you 4 powers and all of them can potentially generate. Additionally, flying charge is a good one (positioning), flanking (have to be already there, but a nice backup attack), formulating attack (initiative change), disarm or strike weapon. Vengeful parry should work, but humility specifies an attack, and not a parry - a worthwhile change IMO.
I would add in war planner, because that lets you get flow during upkeep (though you have to take fairly specific skills to get 2 ranks in war tactics, but there are a couple of options there). Combat Maneuverability is also a good choice here (movement to set up a back attack).
Cloned Maneuver out of the Stalwart can help here (clone a move that meets your Insistences).
also, I don't think there is anything there that says that a magic item can't do the work of fulfilling the condition - just that you have to use an Active Power.
Edit: one I forgot - the Stalo in my group took an Ancestral weapon with a couple ranks of war tactics in it. So, ancestral weapon can help there as well.