I doubt those guys have the skill to do so but for those who do - you'd spend tens of thousands in order to have a port for an old machine that still is stuck with ME and hardware init done entirely by binary blobs.
It is not about the skill or money involved in the process, it is about the *possibility* of even running coreboot on said machine, which is most likely zero.
I would save your money and instead buy an ivy/sandybridge thinkpad (can nerf the ME - but not disable which is impossible)
AFAIK, you can still run me_cleaner on a Broadwell laptop. I don't think the ME is the main reason to get a XX20/XX30 Thinkpad over newer models.
microcode - is optional
I assume you refer to microcode *updates*, not the microcode that is hard-coded inside the CPU. Still, I fail to understand why there is so much worry about microcode updates, as if they were going to open a backdoor of some sorts. To me, the only gain of not updating the microcode is in the number of bugs. I do understand temporarily delaying the updates of known unstable microcode versions while awaiting for a fix, though.
as far as I know its impossible to completely replace ME, only to trim its' firmware as much as possible and hope for the best that it doesn't have some undocumented "backdoor restore" mechanism that could restore the original uncut blob under some conditions. Undoubtedly, Intel ME is a backdoor, e.g. because it contains some antitheft features which could be used to control your computer remotely: shut it down, wipe or retrieve data from it, etc
This makes me feel I should recall what Nico told you earlier: "please don't spread FUD on this list."