The stuff about no branches on the bottom third of a bonsai is intended as a guideline for finished trees, not that they are ever really finished.I read a lot of stuff about No branches botton 1/3 then branches then no branches next 1/3 and no branches crossing eachother and no branches going in front etc. I cut my most important branch while making a chop of the main (front) trunk oops. Nkot to mention the fact that I wanted to make the cut from front to back on an angle downward and I made the cut from bac to front leaving the wound at the front oops.
For trees still in development it is almost always better to leave lower branches. They serve to help thicken the trunk, thereby helping with the illusion of age. Also it is possible that one, or more, of the lower branches can be utilized in the finished design. For instance, one branch could become a new leader. By using a smaller branch that emerges at an angle as a new leader you help to impart movement and taper, two more elements that are desirable.
Ficus can be re-potted 'out of season' since they have no dormancy as such. Summer is probably the optimum time though. If you want R.O.R. then you will probably want to encourage the roots to acquire some length. I have accomplished this by potted the victim, err subject, on an inverted pot inside of a larger pot. The extra length will come in handy when fitting the tree to the rock later.
https://www.helpfulgardener.com/forum/viewtopic.php?t=18867
Norm