I plan to season chicken parts (wings, legs), then freeze, then thaw them out to batter them, and then deep fry them. Will they keep their flavor? Is it safe to do this?
Safe? Yes, of course.
Wise? Probably not.
When you thaw the chicken, the surface of the meat will get wet, from both condensation and thawing ice chystals. Yes, proper handling minimizes this, but it can't be entirely avoided. So when you dry off the meat before battering (which you will want to do to make the batter stick), you will probably wipe off the seasoning applied to the surface too. With "wet seasoning" like brine that is supposed to "soak into" the meat, this will be less, but the main parts will be on the surface as well, as Jolenealaska pointed out in her excellent experiment here.
So seasoning when you are ready to prepare the meat is the more efective way - and IMHO you won't be saving time by pre-seasoning if that's what you are asking about.
I have a different take on this because I sometimes season chicken pieces before freezing them and I have good result with well seasoned, juicy meat.
First, let me say that this practice is safe. Next, people choose their method of seasoning based on their personal preferences or a certain result they want to achieve. Different methods could be sprinkling seasonings on, a dry rub, marinating, or brining. My goal is to get the flavor into the meat, not just on the surface, which is what happens if you season immediately before cooking.
Personally, for fried chicken pieces I sprinkle with salt and sometimes pepper, cayenne, or other spices and herbs of my choosing. I also sprinkle the same under the skin where I can. (I typically use small thighs, approx. 3 oz. each, or small whole wings.)
I then let the chicken sit for 20 - 30 minutes before breading or battering. This allows enough time for the salt to dissolve and the flavors to penetrate the meat. (Some people would say it takes longer but remember that these are small pieces.)
I think this would work well for you. You could simply season all of your chicken, let it sit, then package what you want to freeze and cook the rest.
And while I haven't tried it, I have read that this works with marinated chicken as well.