I did negotiate a deal whereby my leaving (at 52) was officially characterized as “retirement “ and that, under the terms of our plan, meant I got prorata vesting, I.e 100% for the ones due the February after I left (in August), 66.66% of the ones due the year after and 33.33% of those due the following year after that. So yes, I left “value” behind but I felt like I had a deal. But getting it was completely dependent on the plan rules allowing the retirement exemption and a boss who was willing to push for me.
I tried that strategy (or something very similar) and the boss was willing. But plan rules only allowed exceptions in the case of a company-wide RIF... a so-called "bridge" to early retirement for employees between 50 and 55 who were willing to voluntarily retire as part of a company-wide RIF. No such luck for me.