Besides my main channel I had 5 experimental (test channels) - one was for 2D versions of my 3D videos (it was abandoned for 6 months), one gaming, one music and one software reviews/animations channel. Only the 2D versions channel met the requirements of not being kicked out (~4000 subscribers and ~50,000 watchtime hours), the gaming channel was going to be kicked from the YPP (with ~350 subscribers and ~1500 watchtime hours or ~1/3 only) and the music and software reviews channel didn't even meet the previous 10,000 views threshold, so they weren't monetized at all (the music channel had less than 1500 views and the software channel was at ~3000 views).
What I did:
I deleted the music channel (I regret it, but too late). Then I transferred the gaming and software videos to the 2D channel - more than 300 videos, which took me around 3 weeks and I still have to make descriptions for ~55 videos, but there is still time till 20th.
I was expecting the 2D channel to lose momentum because of this rather unusual consolidation, but it still does well and is now at 4100 subscribers. I saw the gaming channel getting some speed after the announcement (people subscribing and watching), but it was going to be a hard race to meet the requirements.
While YouTube doesn't directly offer the possibility to easily transfer videos between channels, I found a fast and easy method to do it, so it was mostly copy and paste work (and losing the videos views, but whatever). If anyone is interested I can describe the method.
Now I can focus on the 2D channel and develop it to 10,000 subscribers, where the real benefits start.