Official MM's For Other Markets.

None of the OMMs do Other Market trades, I think it would be super benefitial(200%+) to the trades in that market area and the scam rate would go increasingly down.

 

Ya they do. A lot of MM's and OMM's do Steam, WoW, and several other trades...

 

Not halo 3, I needed one last night and every1 I asked said no.

 

OMM's do trade for every section, it isn't just related to the Runescape Black Market.
There are hardly any OMM's anyway, you'd be best of using a Mod or trusted user.
For example, Giddy has an Xbox, therefore he's able to do Xbox related trades.
I myself have an Xbox, and do MM'ing, and i know many other trusted users do aswell, for example Toeknee.
Don't always try looking for an OMM, there's hardly any, and it's hard to catch them on, try using Mods aswel if you can't find any OMM.

I find the idea silly

 

OMMs aren't chosen based on what kind of trades they can do, if they fill out a full application WHEN APPLICATIONS ARE OPEN they are likely to be accepted. Its up to the MM about what kind of trades they want to do.