If I remember correctly, also a few gadgets were also backported from Aros to AmigaOS 3.9.
and tons of components can be added or parts replaced. Aros includes AHI, CybergraphX 3, Themeing, enhanced menu, Poseidon, PCI/Support, MESA/Gallium (still slow), Windows can moved out of the screen, impoved memory management and many patches you needed to add on 3.1. You can use both Magellan and Scalos now (my personal favorite is Magellan).
You can add MUI 3.8 easily by basically replace 2 files. WHDLoad works, you can add Wazp3D/Stormmesa and so on. When we talk about aros here we talk about the typical base libraries like dos, graphics, intuition, gadtools and so on. I could bore everyone by continuing...
I am always fascinated how people that certainly never use aros in general and aros 68k in special have such firm fact based views. I could not and would never do that about MorphOS f.e. because I do not own and use it.
As Terminills wrote you can fork aros if you think it is going in the wrong direction and 3.1. compatiblity is main goal of aros (already used against aros in discussions) so Aros devs certainly will not break compatibility just for fun.
Where Aros is slower certainly when doing operations in ECS/AGA, that is visible in benchmarks. Aros was developed for and on X86 with graphic cards so the original hardware never was a goal. Additionally CybergraphX in Aros 68k is a wrapper on P96 so I could very much guess that Aros 68k directly addressing the framebuffer on Vampire is at least not slower than a similar configuration based on 3.X and P96. As I wrote on ECS/AGA that might be different but I think most new software will be written for RTG and to run old software certainly Aros is fast enough (most old games do not use the OS anyway).
So how I see it to go Thomas Richters route:
Pay Hyperion lots of money for the license
Pay the owner of P96 for a license
Pay one or more developers for adapting both (in case of 3.1 you certainly need to sign NDAs what reduces the number of developers being able to do that)
And then you are very much dependent on the owner of 3.1., you cannot fork and develop in a different direction.
Then what is what you pay for? Just a binary?
I do not see any sense in that...