Why have desert Mandos? wouldn't they just be infantry who happen to be stationed in the desert? Our soldiers in Iraq are called Marines, not Desert Troopers. Police Mandos also seem to serve no purpose in the Mando'ade culture.
Why would you say Police Mandos would serve no purpose?
Are you implying Mandolorian culture in anarchist?
I don't know too many civilized cultures that don't have laws - and therein - some way to enforce them. Anarchy and anarchism doesn't work in large social environments - ever. Heirarchies form. Ruling bodies form. Then rules are made. And someone ALWAYS rises who enforces the rules. Its the standard order of human society. And while yes - we're talking "other worlds" scenarios --- one could if not should presume a natural order would likewise arise out of chaos and anarchy.
Maybe "police" is too defining and restricting a concept. Maybe it'd be much better/dramatic for dramatic effect to have a class called: "Mandalorian Regulators".
Maybe they are the "Judge Dredd's" of the Mandalorian culture. Empowered by the ruling bodies. Clan leaders. Elite descendants of Mandalore himself. If you do something dishonorable to discredit the Mandalorian name, or your clan's name - under the "Uniform Mandalorian Code of Conduct" or system however loose it is - and face the possibility of being hunted, captured, prosecuted, and even perhaps terminated by said "Regulators". Maybe they'll just strip you of your armor, your rank, and your clanship --- or maybe they'll send you to serve in a Hutt compound.
Either way - you break the code - you face The Regulators.
I'm just free-styling here with the thought pattern...
I'm just saying --- there would likely be SOME form of "behavior control / legal enforcement" of Mandalorians one would think.