I can look at the options here at a later point. I haven't had much time to think about the future, given that I've assumed the Flycheck maintenance relatively soon. My short-term focus is harvesting some low-hanging fruit (like the package inclusion on NonGNU ELPA).
Compiling a reasonable long-term vision for the future (including some form of built-in interop with Flymake) will take some time and I think it'd better to discuss this separately.