I'm all for integration of multiple arts into your arsenal, so if you can find a comfortable balance between the two I'd go for it. Grappling proficiency will ALWAYS have a place in martial arts, that much has been proven already in a legion of dead horse threads on this and other MA forums. I'd like to add this as food for thought:
Sticks and knives are combat multipliers, to sacrifice something that gives you an advantage like that is a risk (not saying it would be stupid to do it, only that you need to be aware of the risk if you do). If I have a weapon I'd rather not take it to the ground, and sacrifice that advantage, unless I'm forced too (the other guy shoots on me and I'm too slow to catch it, or he's good enough standing up that it's my only option). I am NOT against working stick-grappling, or introducing grappling into FMA. I am only stressing that the advantage to these weapons is more readily apparent and applied from outside of a grappling context. Find the balance between the two and you should be just fine.