As you may know, all medieval armies had a banner carrier.
Make a buyable banner that takes up 3 slots, and gives a stat bonus to nearby teamates for a certain amount of time.
For example, +1 HP for all nearby teamates every few min (which will wear off eventually).
If the banner is loomed, additional bonus's such as a temp boost in Athletics, IF, PS, etc...can apply for all nearby teamates for a certain amount of time.
A text can appear saying "You feel inspired by the banner, you gain +1 Athletics for ___seconds" or some shit like that.