I hope I'm not the only one who hopes we won't be able to buy heirloomed weapons or armor, ever. I know for heirloom grinders it's really nothing special, but I like my tempered long iron sword, it feels special in that I earned it. If I can buy a masterwork weapon for 100k then I'd never retire and just keep making money. I ended Gen1 with 90k, then did an athletics build with light armor, and reached level 30 with around 300k.
However having said that I can understand why someone would want to be able to trade heirloomed items. You start over on a new build, something that is a drastic change from your previous, and maybe that masterwork spiked dildo just isn't gonna work with your archer build. So I guess in that respect I think trading would be ok, but I'd hope for someway to regulate it, such as only being able to trade heirloomed items of equal status.
TL;DR
Buying, no.
Trading, yes.