It is nice to have options for ground battle but in the end they don't influence the battle much.

Here is an example of the same combat with all 3 options:

Forces before battle:

After battle:

They are not the same but the difference isn't much.

Forces left on my side:

  Bombing:  525

  Guerilla:    570  

  Blitz:          555

Forces left on enemy side:

  Bombing:  30

  Guerilla:    45

  Blitz:          45

As I said they are the same but the outcome difference is very small.

One important thing:

  As you can see I don't have reserve forces. I have 600 manpower and I am able to send a maximum of 700 manpower.

That means that the +30% deployment limit from Blitz doesn't give me anything.

So maybe this option should be greyed out if you don't have excess forces?

Cleaner design of the ground battles would be to fold the manpower distribution choices into the ground battle tactics (e.g. pre-emptive bombing is lots of tanks and aircraft;  Guerilla lots of infantry, etc.). You are already making the same choices - you don't need to make them again on a smaller scale. 

An idea exists for this.

I don't want to see anything removed though.

I'd look to add to the system, like attribute bonuses with different choices made to the composition of Armies, and allow empires to be more diverse in how they relate to the available Choices, while also adding modified choices in the process.

Standard options could remain as:

• Bombardment is most destructive with a certain Ratio of Aircraft (more damage to manpower, population and improvements), and least effective with a high volume of Infantry (Soldiers could get caught in Friendly Fire from the Orbital Bombardment).
• Guerilla is most effective with a higher ratio of Infantry and least effective with Tanks (Infantry can better sweep and avoid getting trapped in kill zones, able to reduce enemy manpower faster, Tanks would take more damage as they get focused down with this tactic).
• Blitz is most effective with a high ration with tanks and least effective with Aircraft (Tanks are pushing through enemy ranks and Aircraft risk Friendly Fire incidents).

Then can have a few specialized sets like Cravers have:

• Extermination - replaces Bombardment with a tactic that focuses on Craver Infantry to slaugther manpower and population.
• Enslavement - replaces Guerilla that focuses on capturing manpower and population, sending civilian ships to the nearest Craver planet (think using Spaceport to move population, or a Curiosity Scan that grants a discovered population).
• Assault - replaces Blitz with a tactic where they only assault military targets and Defenders.

Vodyani are another Faction that I can see have something related to an Essense Leech.

• Bombardment - focus on destroying military improvements and defenders
• Essense Leech - focus on sapping Essense violently targeting defenders and population.
• Essense Purge - idea being that Essense is used to destroy Manpower and population, using Empire Essense.

Hope these ideas relay what I mean as to how this system can be expanded on, with whats already there.