I have a lv50 Shadow and a newly lv50 sage, and I was wanting to give my old mods and stuff to my sage so that i wouldn't have to grind dailies. The obvious problem is the items are bound so cannot be mailed direct to my sage or passed via gtn. So I bought a pair of legacy boots from the vendor on coruscant, put the mods, armor and enhancements into the legacy gear and posted it to myself. Now as a method to transfer stuff this is pretty expensive, you have to pay to remove mods from old gear, buy legacy gear, then remove the mods again (assuming you aren't going to use the legacy gear), not to mention 5 credits to mail it! If you wanted to transfer columi or rakata stuff you'd need to buy all 5 main armor pieces too (for the armoring), plus more mailing costs (use tionese shells to get the set bonus back if you really want it ).
So onto my point, how about a unique (to legacy) item that can contain a bound item for mailing. Like an empty lockbox so the mailbox doesn't see the item is bound. The item would be bound to legacy so you would only be able to post stuff to your alts. You could make the item quite costly so it wouldn't be something that came too easy, so about 1m credits for the item and a mailing cost of 1000 per item.