For quite a large part of the Medieval era, surnames tended to be quite rare, especially for the poorer people. For one, communities tended to be a lot smaller, so there'd often only be one or two "Harolds" in a village, for example. Removed the need for surnames at all in a lot of situations, so it'd be pretty difficult to find many truly authentic Medieval surnames that suited a character's class.
Furthermore, with Aloria's fantasy setting, it's kind of unnecessary. A lot of the most creative and memorable characters on Massive have names that hold little resemblance to any historical name, and I think this type of original character is part of what makes this community what it is.
There's no real need to enforce such high standards of historical realism on a fantasto setting with loose Medieval influences, in my opinion. It'd limit more than improve, I think, even if it was feasible.
None of this is intended to be insulting of anyone else's views or anything, and I don't claim to be an expert on Medieval naming systems, either. Just my input on a matter that sparked my interest.