I was looking into this last night as I have won (via greed rolls) a couple of pieces of Rakata / Columni that my main cannot use, but an alt can.
I went to check out the cost of the legacy armor and it is a bit expensive. 50 - 250k a piece.
So, this gave me a question. Can you buy one piece (doesn't matter for what class) and put mods into it from any armor that you stripped and send this on to your alt? Or do you need to essentially have 1 piece for each slot to ensure the armor mod will 'fit'?
If it is option 2, then are you again restricted to making sure you have all the legacy armor for all the classes? OR is the restriction not that tight? i.e. If I have a SI leg piece, do I have to put it in a SI legacy leg armor? Or can it go in a SW leg armor?
Then across factions opens up a bigger can of worms.
It doesn't matter which class, but the armorings from Tionese+ gear ARE slot specific. The one exception is offhand shield armorings. Those will fit any piece, including belts and bracers.
You can even send legacy bound gear across faction, provided you didn't pick a long gibberish name even you can't remember how to spell...
Obviously, your Sage won't be able to wear Sorcerer gear, but the mods will work.
There was also a new twist added with the last world event. If you bought the blasters or sand people armor, it is legacy bound. The SP armor and the set from the Rakgoul event last spring are NOT class specific, so it can be passed around and worn by anyone and even companions.
The blasters still require the appropriate weapon skill to wield. And they will not accept Hilts, so there is still no way to transfer saber hilts across legacy.