I use Gramps as well (love it actually) and also mark profiles that I have found with the WT URL. So one side of the screen is the relationship manager in Gramps, the other is the GedMatch screen of Wikitree. I use the person IDs then to see where I am.
It would be great of the import of GedCom would use the extra information, and it shouldn't be too hard. (But I am not programming WT). I personally use the Notes field, type 'link' for the WT URLs.
To be honest though, I think that Gramps should be taught to deal with information from Wikitree. That can be done with a Gramps Widget. Why? Because Gramps is really nice for research (no LNAB troubles) and Wikitree is really good for showing the results of that research.