Asst. PM Roles

I have an opportunity to join a fund as an assistant PM and am hoping to get some advice on structuring the role as I have a fair amount of input. For context, I have ~7yrs buyside experience, almost all in a hybrid public / illiquid credit and special sits capacity, and am currently a sr. analyst responsible for all levels of idea generation, managing buy / sell levels, and running point on deal processes at a different fund. The role would be focused on several different pools of capital across both drawdown and daily/quarterly liquidity vehicles. 

A senior PM will be above me with final discretion, but the idea is for me to eventually takeover after several years in addition to assuming responsibility for firm level strategic activities as part of longer term succession planning. Its hard to find much out there on assist. PM roles and from what I've gathered they tend to be fairly nuanced. My question is, what sort of things should I ensure are optimized to truly differentiate this role from a standard sr. analyst and build PM experience? The senior PM is a mentor figure I've known for years and would like to work closely with me so the job description has room to flex in my favor. I don't expect a payout-based formula for comp, at least not right away, but solving for highest comp isn't super important to me right now as much as making sure I get the right experience is. I am < 30 and think this is a fairly unique opportunity with a lot of runway, so the comp should work out in the long term. Want to be careful of not just stepping into a different sr. analyst seat with additional admin work that doesn't build into PM experience.