Pro-strat: Ban quick fix, medigun, vaccinator, kritzkrieg, and amputator. Meds can only heal with the the crossbow. 9v9 with no heals aside from engy.
edit because I skimmed over the HL part. Didn't expect it to just flat out describe HL instead of saying HL.
Also, you could ban every medic primary too, forcing the med to be melee only.
EDIT2: Actually it might be cooler to allow only the Amputator and ban the crossbow + mediguns, since the medic becomes a sitting duck whenever you want to heal.