Kind of an out-there suggestion that I doubt will be seriously considered, but it could be used to stretch out the relevance of ground experimentals.
Rather than making the experimentals simply better through increased DPS or health, the experimentals are made into much more versatile units.
Here's some ideas for what this could look like:
Slot 1: Air factory | Improved engines
Slot 2: Advanced AA (aircraft carrier grade) | Tactical Missile Warfare System (equivalent to four TMLs and TMDs, builds TMs with reduced price and damage and scatters when launching a volley)
Slot 1: Disruptive Beam (beam has increased shield damage) | EMP Overcharge Cannon (manual/auto fire like ACU overcharge, requires a huge amount of energy to recharge)
Slot 2: Rapid Reclaim System | Rapid Capture System (tractor claws reclaim/capture units at a very high build rate)
Slot 1: Incendiary AA Artillery | Portable Gateway (moving units to Ythotha teleports them there at the cost of energy, with enough energy you can even move experimentals)
Slot 2: Amplified Detonation | Tactical Nuke (Like Billy)
Slot 1: Stealth field -> Cloak Field (no self-cloak) | Stationary Fire (improved range when not moving)
Slot 2: Bubble shield | Radar Jamming
Slot 1: Flak Battery | Long Range Missile Deflection
Slot 2: Artillery Guns (similar to three gunthers but with 100 range) | Advanced Engineering Station (equivalent to two maxed out hives with double range)
Sounds like a fun mod. Do you have experience with coding/ 3d modeling? With some knowledge this sounds doable for one person.
the Coding side of this is not the hard part. it more the Adding to the Exisitng Model and bones for the addisional Structuers
I've read somewhere that in SC2, some experimental functionality comes online before the thing is completely finished building
So it would be interesting to have, let's say, a spiderbot that can start walking before the cannon is ready. So you could keep it in the base while you assist the laser upgrade. Or you could send it to the front and the spider would finish building the cannon on the way. That would get it out the door sooner but it wouldn't help you to defend a base sooner. So it would essentially reduce build time in some situations but not others.
Or a different approach, when the GC finishes building it has a movement speed of 0 but a fully-functional cannon. Then you assist it with the "movement speed upgrade." When that finishes, it can start walking. So you could use it essentially as point defense until you finish making it. I see all the time people scrambling to finish a GC while enemy units approach. It would be interesting if the GC could shoot at them while it was finishing.
Since these upgrades would be only a net positive, they would start building automatically when the unit finished construction.
hey could be paused if you don't want to spend on them but they couldn't be canceled.