1. Abandon the silly ban on HP ammo. That notion was based on flawed medical science and flawed battlefield tactics. HPs stop threats faster, which decrease suffering. HPs offer less over penetration too.
2. Stick with 9x19 (cost, availability, weight/size/capacity, recoil).
3. Pick an off-the-shelf tried and true weapon and go with it - Glock, Sig, CZ, SW MP, XD, whatever. ZERO need for testing. None. Nada. They work. They are rugged and reliable. Good enough. Extra credit if it's a polymer gun for 1 pound weight savings.
4. Negotiate or open bidding for the best 20 year contract per piece and servicing/warranty/replacement contract.