If you have a Maneuver Master (and let's say you dip Fighter to get heavy armor proficiency,) is there anything stopping you from using Flurry of Maneuvers while wearing armor and using a shield?
For reference, the Monk class specifies:
Armor and Shield Proficiency: Monks are not proficient with any armor or shields. When wearing armor, using a shield, or carrying a medium or heavy load, a monk loses his AC bonus, as well as his fast movement and flurry of blows abilities.
Since Maneuver Masters don't have Flurry of Blows, by RAW if they are wearing heavy armor, they lose fast movement but can still use Flurry of Maneuvers?
yes, the flurry of maneuvers is a different ability from flurry of blows and does not contain the wording prohibiting its use in armour. Monks not being proficient in armor isn't actually relevant to this.
Why stop at dipping Fighter? :)
I'd do no more than 6 levels of MM Monk and all the rest in Lore Warden to get big bonuses on CMB. The 2nd and 3rd maneuvers in the flurry have utterly staggering penalties anyway.