Is it possible to spend a couple of years after a post doc working as a bioinformatician and then return to academia?
As long as you are doing your own research and publishing, I don't think this should necessarily be a problem. If the position is de facto similar to a post-doc with a higher salary you should be fine and it will probably just be treated like a second post-doc.

However, if you are just giving services and not leading any research project that can be a problem.

So the bottom line is what matters is mainly what you actually do and less the title of the position - I know of someone who after completing his PhD took a bioinformatician position in academia, rather than a post-doc, and used that to get a faculty position.