One thing I remember from GalCiv2 is that I never ever used invastion methods that damage Planet Quality. Free space have been such a precious resource that it was million times easier to build more invasion ships than to lose even one tile.

Then, if you have to take small planet of 6 or so tiles, then losing one to three  tiles will effectively render it worthless.

So, the only viable invasion tactics I saw was the ones that left PQ intact.Entire swath of invasion options were ignored alltogether.

If developers intend to stick with that approach of damaging PQ, then maybe there's a way to make such invasion options at least somehow appealing.

For example:

1. Natural restoration. Lost tiles could be restored after certain amount of turns in a way of "nature healed itself". So player does suffer in a short-term by losing access to polluted\ruined tiles but in a long term will regain it and thus preserve the value of the planet and still have bombardment as a viable invasion option.

2. Bombardment and other PQ damaging types of invasions could be changed into low cost- high damage options that does not completely cripple the planet.

For example after bombardment lost tiles could be deignated as ruined\polluted etc. And some early ecology tech could be used to reclaim lost tiles. If you do not want to wait for natural restoration then you could spend money to speed up the restoration via buildings(akin to adding new tiles in GalCiv2)

3. Make technologies change invasion effects. Chemistry advancements could make Chemical warfare less PQ-damaging and so on.

All this should serve the main purpose - make all invasion tactics a viable options and prevent GalCiv2 situation when 90% of all available options are never used.