Ill be honest, I think it has less to do with technical limitations ( although as old as the original game engine is at this point I'm sure there are plenty ) and more to do with them still debating how they want it done. Do they want it mailed or would they rather move it through an account wide bank? Would making it be achievement based be a better solution or would they like a different functionality?
So lets say they decide they want to do more than just make a drop down window, or a system that requires you to use an outside website, but would rather do it through mail or an account wide bank. Ok so now they are sitting there looking at both options and realizing if they are going to take the time to change what they currently have for one item set, they might as well completely overhaul the entire sub system. Well now that you have decided on that you are talking about a pretty decent amount of work, and its something you've got to work in with the other things you have scheduled to include.
Alright so now all of those things are handled and you've got it ready to go for testing. Now comes the fun part of making sure its not buggy and people aren't losing items that will cost you CM time to fix. You also need to make sure its not set up so that some uses it to dupe items or because its brought in with an entire system overhaul that it doesn't throw server economies and such off.
Its just my personal opinion, but I think its something they want to solve through the CRZ functionality, they just haven't gotten it done yet. I have no doubt they want to get it done at some point because its obvious customers want it, its just a matter of getting to it and getting it in how they want it.
I'm an altaholic myself, and while I would love to see it implemented sooner rather than latter, leveling new characters on a new server isn't exactly that hard either. I personally get far more frustrated with having to start at zero gold again ( although thats not as hard to deal with as it once was either )