I went searching the OpenWRT forums and wiki for recommendations and ended up with the GL.iNet MT-6000. The stock firmware is a gui around a modern OpenWRT and they don’t try to lock it down at all so flashing is easy.
Thanks, I ended up going with this one. Looks like there's a new Flint 3 coming, but rumors seem to be indicating it is going to be more expensive and is possibly not OpenWRT compatible due to chipset. So, Flint 2 it is for now.