@thewheelie Thanks for taking the time to explain.
While you mention it was a trap to begin with to build SACUs, I'd note that particularly at lower ranks the Seraphim SACU was a decent unit in its own right, since it provided you with flexibility even if it didn't excel at any one area. It gave a mini-RAS effect, had enough build power to get SAMs to protect from air with enough health to get near the frontline where engineers would just die, if the enemy didn't kite them would have enough combat efficiency to break through a slightly smaller force, could get upgrades (particularly the TML) to surprise the enemy, and could get reclaim near the frontline. They'd be worse for any one of those roles than anything specialised in any one of those areas, but could be a 'safe' option in some scenarios. Now they'll clearly be a bad option to build, so the pool of semi-viable units gets reduced from these changes.
In terms of how to have the base SACU decent without making the other upgrades overpowered, an alternative way of achieving the same goal but without making a number of already rarely seen units become even worse could be to reduce the SACU mass cost and then increase the cost of upgrades to compensate.
For example, taking the Seraphim SACU, it's health is being reduced from 15.5k to 11.5k, and its dps from 400 to 100, so it's had a massive reduction to its combat power with no change in its cost, and it wasn't overpowered originally. Trying to balance by decreasing its cost and adjusting other upgrades while not perfect (since sometimes they'd get multiple upgrades) could still give something that makes the base SACU less terrible, especially as for many upgrades you'd want ot be getting multiple upgrades together for it to even be worthwhile. As an illustration of an alternative for the Searphim SACU (similar logic would apply to the others as well):
- Reduce mass cost from 2050 to 1050, build power from 40 to 30, energy yield to 100 and mass yield to 1 [References to mass cost changes would have a similar change to energy cost].
- Adjust enhancements that would be problematic with this cost (taking into account the planned boosts to some of these), i.e.:
- DamageStabilization - Current changes are set to increase health by 7500 to 18000 and give 250 regen for 2500 mass - as a standalone upgrade I dont see this as being that powerful, you'd want to combine it with a damage boost for it to have a noticeable impact, so only needs a moderate cost increase of say 500 to 3000
- Engineer - Currently set to cost 380 for BP increase from (nerfed 40) to 98 - increase the cost to 1280 (with the above reduction in eco benefits it'd end up in a similar position)
- Sensors - Increase the cost slightly by 300 to 1100 mass - most of the time you'd be wanting this on a unit with other upgrades given the range boost
- TML - Increase the cost by 800 mass - you'd usually only be getting this upgrade on its own before and using the unit as a mobile TML to surprise the enemy, but for such a scenario you're more likely to be having the SACU near a frontline position where its previous combat potential would have been of use
- Overcharge - due to the massive existing cost of this you're only going to want to get it with other upgrades that improve the range and/or durability, so I'd give it a very small 100 mass cost increase
- Shield - Currently being made 1200 mass for 24000 shield - an upgrade that you'd only really want to be combining with combat upgrades, so I'd increase the cost by 400 mass
i.e. currently the planned changes would heavily nerf the base SACU; the missile preset; and the combat preset. With the above changes, all of these would have the nerfs significantly reduced or potentially be comparable with their current power-level. There would be a very slight boost for the nano combat preset (-200 mass but offset to some extent with a loss of resources and BP), and a slight nerf for the rambo preset (no change in mass cost, but a slight loss of resources and BP) - obviously the costs for the upgrades could be adjusted further to achieve a different outcome.