I don't see anything weird about it. I've been increasingly mixing more PHP into AJS 1.x for some time to over come it's short comings and make some loading times faster, etc...
No language or framework is perfect, least of all AJS (or PHP for that matter), as a developer, right or wrong, it's your job to get the job done as best as you can. If it's using AJS and Rails - ok. Write good, clean, well documented code so the next person (if there is one) can maintain it, but so long as it makes sense and works, go for it.