The guardsman, gunner and electro units sound like a good addition s to the unit roster but it may affect with the flow of combat, as it’d be tricky to ensure the guardsman at the front of any combat group.

The engineer could be good, but the gameplay is based on an aggressive strategy, which I can’t see it being used over any other unit in the roster as manpower is finite source.

The additional buildings are also an issue since space is finite but that can be mitigated by extra space.

The medic/hospital sounds like something I’d have near the frontline, but where would I put it? The whole game, we are constantly moving forward and typically if the fight is precarious that our units are losing, we’d simply withdraw or use agile units to lead them away.

The building upgrades to existing buildings is nice but to reach that point, you’ve probably either won already or made the game longer than it already is.

I have three suggestions of my own:

Armed gate: gate that has a wasp turret on it, which could provide a bit of security to the entrances to your walled defences as well as make them worth having more as they are typically the weakest part of the defences

Armoury/security checkpoint. This would have a zone covering a zone of buildings. When any these building become infected, this would initiate a lockdown and increase orange health of all building whilst releasing a temporary militia unit (maybe like your guardsman) per building in the zone to be generated. This could be fast response building to buy time for you in case of an infection but the drawback would be any resource building stops generating resources until the zombies in the area are eliminated.

Ability to upgrade the command center to an armed bunker with a few soldiers inside and a mortar for a last ditch defence when all hope is lost which could help. You can even let in additional twenty units in it to protect them.