What are your thoughts about "Research Assistant Professor"?
I don't think there can be a general answer about future outcomes for a position like this. It seems like a bigger investment for the department than a typical post doc spot, though, which may be a positive.
I would look at the history of the position in the relevant department. Are there tenure-track faculty there that came from this path? I'd also ask current tenured faculty in the department, not just in leadership, for their candid opinions on the future of tenure-track slots in the department. It might be that these positions exist for political reasons that make future tenured spots unlikely, or it may be that it's a good introductory role.
Good luck.