Is there the option to refuse a MD WC and ask for one to qualies? I can see where for someone like Heather Watson, who is a really strong player but underranked because of just coming on the scene, a MD WC to a big tournament is a good thing: she has quite a good shot at winning. But, as people here have said before, if you are working your way up and are at the level where you can beat someone in the, say 150 to 300 level, but haven't ever beaten a top player, is a MD WC the best idea? Or could you choose to go for qualies, with the lovely points on offer and people closer to your own rank?
I can't see any issue with refusing a MD WC if you can get into qualifying on your ranking. Naomi Cavaday apparently did that for Wimbledon last year, saying she wanted more grass court practice. I did also note at the time that she had previously won some rather useful GS qualifying points so was maybe not unmindful of that
In the more unlikely situation that you'ed need a QWC I presume it's just a question of asking the particular tournament.