Heirlooms are good in my opinion, as they not only reward dedication to the mod, they encourage players to "achieve" something. It gives new players something to strive for. This was really emphasised when Final_Boss released his heirloom texture pack. I know I would just trade looms around to see how they looked in-game, and that's what kept me playing for a while.
And yes, in regards to the original post, looms are common, which is not a bad thing. They seem to have had a pretty steady price/value over the past year, with only minor fluctuations being in loompoints.
So all-up, a loom-sink would have both, positive and negative effects. It would help balance, as the veteran players wouldn't have such an easy time slaughtering the masses (say if it was a loom limit for a gear set), and make the game more skill-based, however, it would make the game drier in a sense, because if you have a favourite gear set, you won't be able to use it.
And Torp, you have not really mentioned the marketplace. People have the mentality, that why bother with looming gear, when you can trade for it anyway with your current looms? The marketplace this way allows people to use builds, and just trade looms, as opposed to retiring. Kind of seems like a passive loom-sink to me in a sense.