Maelstrom

more than 128 upgrades is possible, I've been doing it for years, but there are exceptions that you have to make.

It works best with "Object Upgrades" such as overlord add-ons or drones. You can replace their usual cameo with a generic and rename them as "Unit Upgrade". then you can use the same upgrades on several units anywhere that price and build time is appropriate. Just consolidating your unit upgrades can make a huge difference in how many "player upgrades" are available.

There are additional workarounds for player upgrades as well, but they have their own drawbacks... though on the flip side they also have a couple perks. I'll be upfront, the drawbacks are: No Upgrade Cameos on units. Buildings/Units that purchase player upgrades must be immune to capture (or they can be exploited). This can sound like a big price to pay, but the perks are substantial.

The benefit is you can have 128 upgrades for EACH faction. Additionally you can build objects that grant the upgrades when complete. (make sure you have build limit 1) This lets you use prerequisites on your upgrades that are normally restricted to units, and even when you lack a "normal" cameo you can still have the correct icon appear in the build list while you're waiting for it to build. You can also use an upgrade from any other faction while keeping a faction specific cost and build time. One last perk about this method is you can make certain upgrades exclusive to each other... ie: you can't have Upgrade B if you chose A or vice-versa. You can do this just by giving the same "MaxSimultaniusTypeKey" type to upgrades you want exclusive.

This method is how I have my mutually exclusive trees working in Remix.

As a side note, you can use the upgrade objects and get all of those benefits without using overlapping upgrades between generals. This way you have all the perks without the compromise.