>>23609718
>0079 straight to Unicorn. 00 and Wing. Almost halfway through IBO. Maybe halfway through Seed. Did Astary and Thunderbolt.
In that case, you should have access to a bunch of SR and SSR units that can fly, but I guess you might not have developed them. All of the GN-powered MS in 00 can fly. Unicorn has some flying units as well, the Byarlant 01 and transformed ReZEL Defender B have attacks with 4 range and decent damage.

If you 100% completed the development trees for the above series, you should have unlocked the free ULT units for them too. Unicorn's ULT is the Delta Kai (>>23609591) and its transformed flight mode is actually really good for damage. Wing's ULT is Aquarius, it flies and has a 3-5 range attack which isn't bad for damage either.

Have you also been doing the Fierce Enemy Attack events? Red Gundam 0085, Saikoro Gundam, Destiny Impulse and Byarlant 02 can fly. Destiny Impulse and Byarlant 02 can dish out quite a lot of damage.

>Also do the event rewards return though?
Yes. Every floor you clear will have diamonds + one other thing as a reward, except for floors 14 and 19 where you get a free UR pilot instead. The next time the tower comes back, progress resets and you get to climb the tower again and receive diamonds + one other thing as a reward for clearing each floor again. So even if you don't progress much, all you're missing out on are diamonds and some dev materials. You will always have the chance to try again for more diamonds, mats, and any UR pilots you missed the last time around.