Hi,
Interesting questions!
Well, first you need your cycles back. They may return before 12 months anyway. If not, you may well have to cut back. Some women do find they have to stop entirely, but very often cutting back to 3-4 feeds in 24 hours (or something along those lines) will do the trick.
I cut out night feeds at 14 months and gradually cut back day feeds as well, and AF returned at 16.5 months.

What are the drugs that are no good while breastfeeding? I know some women do have to take some rather nasty stuff unfortunately. The general stim drugs etc are ok, BUT they will affect your supply. You may find it's an effort to keep the milk going, but personally, I reckon it could be worth the effort, especially if (hopefully not!) the cycle does not work. That was my greatest feear, weaning and then still not being pregnant.

DS was on 1 a day when my FET cycle started and after a week on progynova the milk was gone. DS kept 'feeding' till I was 8-9 weeks pregnant however. Whether or not your plan can work will depend a lot on your child - if he's dead keen and not ready to stop, then you've got a much better chance.

All the best with your forward planning!