Accepting a postdoc position (in a different field) after industry After a PhD in Biomedical Engineering (focus on Imaging and Robotics) with a decent publication record and some prestigious fellowships, I took on an industry research position at a well-known company, where I've been for 1.5 yrs. Still, I've kept one foot in academia with the goal/hope of one day returning (for the usual reasons: opportunity to do longer-term research, publish, mentor, etc).

Specifically, I've been collaborating with a well-known PI from a different field (Neuroscience) who needed help with a "side-project" (applying machine learning and related techniques to complex neuroimaging data). The project has gone further than expected, and we are close to publishing a paper. I expressed interest in continuing this work and, to my surprise, he invited me to interview; it went well, and I've been offered a postdoc position. Furthermore, since he lacks computational expertise, he wants to set me up with a co-mentor who is renown in the machine learning field.

I'm looking for opinions on how risky it'd be to make this jump. My concerns are:


Field change. While I've taught myself a range of computational techniques through this project (and through my industry
job), my prior publications were not in this field.
Neuroscience is even newer for me. Even assuming a productive postdoc, I worry about my
competitiveness for future TT positions compared to people
who did their PhD's in these exact areas (what do I bring that they couldn't bring?). I'm also concerned
about my CV appearing disjointed.
The mentorship situation, since the PI himself is not a computational     expert. The people in the co-mentor's lab are experts, of course, but I do not know them as well (yet).


Reasons this could be great:


I get to do more long-term, basic research in an area
in which I've always been
interested.
The main PI and I have worked well together, and he is genuinely interested in mentoring me, helping me apply for postdoc/early-career funding, establish independence, etc.
If the co-mentorship situation works out as planned, I'll receive great training from both sides.
Hopefully by having a head start and being close to a paper
already, I'd hit the ground running.


My options are pretty straightforward: Say no and continue my current industry job; say no and start looking for strong postdoc labs closer to my area of expertise (or another industry research position that prioritizes publications and longer-term research); or jump on board and swim!

TLDR: I'm "stuck" between two good options - terrible situation, I know. Still, I've been on the fence, as it's hard giving up a permanent position in industry for a risky alternative. I'd like to know if my concerns are valid, and I'm curious what others would do in my shoes. Apologies for the overly long post, and thanks very much for the feedback!
As far as I know, there no specific field for postdoctoral researchers. A project may require experts in different fields, where machine learning, image processing are highly needed in interdisciplinary fields (e.g., medical image processing). 

In my opinion, you should respond to these questions before accepting the offer: 


Are you an expert in the domain of the position (regardless of the boss's field) and do you fulfil its requirements?
It is important to note that as a postdoc, you will be responsible for your work and you won't be supervised in terms of your knowledge. 
Does this intersect with your PhD in terms of research domain? 
Usually, researchers do not know their exact subdomain based on their PhDs (which is more likely to be in several subdomains). For example, working in Imaging and Robotics can be considered as "Image processing", "Machine learning", "Artificial intelligence", "Pattern recognition", etc. I would say, any position in one of these fields will be accepted for postdoc and thus will define more the research path in the next years. 


If you take a look at the research interests of any senior researcher over time, you will find slight changes. 

I am also doing my postdoc in your field, but it is totally different from what I have done during my PhD. However, I could find a common subdomain between the two experiences and I decided to continue in this direction for the next years.