The long term plan for sacu's is to make the presets more specialized and more viable to encourage different kinds of sacu upgrades throughout the game. For example having viable engineer presets, viable combat presets, viable army support presets, etc.
One of the main reasons for nerfing the current base sacu statline is because it makes certain paths obsolete. For example you barely ever need engineer presets because a rambo sacu can just throw down a sam right at the frontline in 10 seconds. Since you make more than 1 it means you have insane bp in your combat units at the front making engineer presets useless.
Hp and damage have the same reason al be it less impactfull. A good example for this is when a gc walks into a ras boy farm and dies to ras boys because 8 ras boys have the same dps as a gc, which makes no sense at all.
Therefore the basic sacu hp dps and bp will be nerfed, but the upgrades will be balanced out to negate the effect. That means that shield and nano upgrades will give extra more hp that was removed from the base statline, same for the engineer and gun upgrades.
There was an option to choose to make it work in reverse. This means keeping the base sacu as it is but making certain upgrades lose you different stats. Like gun giving you reduced bp, or engineer/ras giving you reduced hp/dps. There are quite some problems with this however. First of all it's gonna be very clunky because what if you manually upgrade your sacu to have both ras and engineering quite? Should it lose double as much? It's also very unintuitive when players upgrade their sacu and then it becomes weaker in areas. There isn't anything like this currently in faf so we felt like it wouldn't fit in.
The 1 downside of this all is that the base sacu becomes even weaker than it currently is but it was always a trap to begin with. It has always been bad to make because it is not specialized in anything. It's bad to use as bp cause why not use t3 engineers instead. It's bad to use to fight because why not make actual combat units instead. It would be nice to have it be decent, but so far none of us could think of a way to make it work properly.