This is a study that I have wanted to do myself also, and have slightly started on.
A problem is that I am still waiting for record sheets of several crucial early mechs, most notably the Orion, the Archer and the Griffin, which are among the ten first mech designs that we know of.
- There is no way the Striker would be the first assault mech.
- Bellerophon was the first heavy mech, but it was a failed design. So, it is probably that the Orion is the first heavy mech that saw general deployment.
- Kyudo is the first medium.
- Commando is probably the first light mech.
As for dying off, I can not really come up with any old design that has not in some way influenced newer ones. Still, there are very influential designs, and those that has made very little impact (like Helepolis and Eisenfaust).
EDIT:
Would all "upper end assault mechs" (90 tons and above) be considered evolutionary descendents othe Mackie?
would all "lower end assault mechs" 80-90 tons) be considered evolutionary descendents of the Stryker?
A) The Banshee has also heavily influenced the upper end assault mech.
B) While 80-85 tonners were uncommon during the Age of War, both the Longbow and Victor are older.