Generally, I find 'achievements' pretty lame, in most games they symbolize either weak gameplay that requires filler, or a gimmick to attract people who aren't actually interested in the core aspects of the game in the first place.

That said, honor needs work. Viability of this idea would depend on whether you can get a large, diverse enough list of things for provinces to do, such that all the current playing types will feel like they have something to gain from this. (hit a province x% bigger NW than you, x% bigger acre than you, gain x% acres from 1 hit, gain x# sciguys from single abduct some examples?)

Would you be able to perform the same task more than once per Age, or YR or something like that?

I think under a system like this, rather than having achievements that could be lost resulting in lost rank, that your rank could be determined relative to the rest of the provinces on the server. For example; at the start everyone is at Knight, once achievements start to accumulate, provinces receive some sort of points, and once the gap between highest and lowest # points reaches a certain threshold, initially that one province becomes the first Lord, and others who pass that threshold will join him/her in their Lordliness... once the gap between highest and lowest get to the next threshold the same thing happens with Barons. So, if somehow every province on the Server did every achievement they wouldn't be Princes, they would still all be Knights because they have 0 achievements relative to each other.

In this way you could still have people moving up and down honor ranks, but it would be much more stable. Might hog the server though I guess constantly updating that