Stern would do itself a huge favor if it made code improvements for their VE releases to reinvigorate interest in the game. As mentioned, DoD Multiball and skill shot are obvious issues, and I didn't see anything in the recent IM code release that is useful for existing customers.

Unless you are referring to IM Classic, this is just not true. IM Pro is has the same number of features as Pros made made today.

How many other games created in the last 5 years are more relevant than IM and have incomplete code? (Ignore those released in the past year... Stern always takes 1.5 years after release to complete code)

You basically made my point: IM is as good a candidate to finish off as any other Stern game made in the past 5 years... with the following exception: When Lyman is the only coder, count on it being completed at some point. With IM he was only part of the team.

Complete is a relative term. You can chop out DoD multiball and Jericho and the code will still be complete. ACDC was complete before the last few updates. I get the argument that IM wizard mode should remain difficult, but I'm not sure the near impossible classification is ok... and there is still no earnable extra ball or real skill shot. I'm baffled anyone doens't want at least a minor rule update for a game actively in production, especially considering Stern has 4x as many programmers on staff as they did when IM was created. This is the kind of thing someone can do over a lunch hour.

For better or worse there is an intended stacking order you have to abide by. As you said you can start War Machine with Monger up but Whiplash can never be stacked with Monger. You can stack War Machine with either Whiplash or Monger only if you start War Machine first. If Monger is up when starting War machine you can stack with Monger but not Whiplash, and if Monger is down when starting WM, you can stack with Whiplash, but not Monger. This just adds to its challenge and mystique

It wouldn't make sense to allow Whiplash progress if Whiplash multiball cannot be achieved.... which goes back to the stacking rules.

Sad to say it but because Lopp did the code with Lyman, any possible refinement is going to have to involve Lopp making the effort. Lyman is the only one at Stern with a strong track record of refining late stage code, but that's always with code that is all his own.

No one ever legitimately reached DoDMB, correct?

The perfect time to do this was when they were already tweaking the code to create the VE. I honestly don't understand why they didn't tweak a couple rules at that point to benefit all owners. It was short sighted, but consistent with their history of code updates (Lyman-owned code excluded).

Lyman only polishes code where he is 100% the author. Lopp was co-author of IM, so that pretty much ensures Lyman won't touch it again... and neither will Lopp.