I think a combination of jits and strength conditioning would be optimal. You can strength train hard for 3 months, but if you don't keep up with it after the three months you will lose whatever gains you made, not to mention being a bit rusty when coming back to jits. I would suggest weight training on your days off from jits. Also, weight training can shorten muscle length, and unless you are really stretching properly and often, you may lose some flexibility. If you do both you will be able to keep the flexibility up by just going to class and stretching when you are really warm. It's hard to get your body as pliable as it is after training jj.