I contacted Arca Noae about this time last year when I was moving forward toward writing my open source OS/2 kernel replacement. They were very non-receptive to the idea and it was a difficult email exchange over a week or two.
Well, first off, the kernel is not likely to be a short term project, and AN doesn't have the manpower to manage such a project over the longer term. If you want to do that, and present them with a working kernel, I expect that they would look at it. The main problem being that it would not be certified to the required standards, demanded by many of their customers. I doubt if there are enough OS/2 users left to be able to pull that off. It is also much more important to add things like USB 3.x and WiFi, in the short term, so that people can actually use the product. AN do need to get the basic OS running well enough to keep their customers happy, and that must be done in the short term, with very limited manpower. It must also be done with no possibility that somebody else will claim that their work was copied, or, they need a complete disclaimer that all work is original, and they have full access to whatever is presented to them. They do have contracts with IBM, other software vendors, and customers, that need to be followed. They cannot take any chances on something like a new kernel, that may, or may not, work as expected, in all cases (and they do understand just how difficult that project would be - I wonder if you understand that). It is difficult enough to get enough testing done on things like NIC drivers, to keep customers happy. Writing software is only the beginning of what needs to be done to add parts to a commercial product that may be used in military, and health care, situations, where no failures can be tolerated. Small steps are necessary, to keep OS/2 alive, in the short term, and there aren't enough people to do long term projects, never mind get them certified.
To write a new kernel, you need to start with a description of ALL of the things that you expect it to do. I honestly doubt if anybody on earth could describe all of the things that the OS/2 kernel does. If the new kernel is not 100% compatible, it really cannot be called "OS/2" (in fact, AN uses the name ArcaOS because IBM forbids using "OS/2"). A new kernel that can run OS/2 programs would probably be accepted by a lot of users, but the main, core, customers would not be able to use it until it is properly certified.