[Alneyan]

I would advise against putting your whole fleet on "Don't get hurt", as your ships can end up acting weirdly. I recall a "battle" where three of my vessels were on Don't get hurt, but ended up being shot down by weapon platforms. I think you are likely to run into such problems if you are attacked several times while orbiting the planet. Of course, it may have been a glitch in my strategies, which wouldn't surprise me.

Blockading the homeworld is however a very good step (how you do it is another matter), though you will likely have to shut down trade income as well. If you can deny the foe any resources, you will eventually deplete their storage of resources (eventually), and especially intelligence. I am not sure if the Planetary Cargo Damage project works in Proportions (it is broken in the vanilla game), but if it does work, it should be a nice help to destroy all these weapon platforms. Having allies doing some intelligence pummeling to get rid of that Counter-Intelligence would help as well.

Otherwise, I am afraid several waves are virtually mandatory, but if you can prevent them from building any more units, you should win the day, sooner or later. More specifically, planetary bombs should do a lot of damage to the cargo, and will not have the punch needed to glass the planet, even if too many of them are dropped. That should also take care of the troops stationed on the planet (if any are there), but the militia will still be there to fight. I am not sure how powerful the militia is in Proportions though.

Alternatively, something involving a swarm of units might do the trick: units do not have maintenance, and you could probably send a host of well armoured units in the vangard, taking hits away from your ships dealing the damage.

On "not exactly conventional weaponry", you could be creating some storms over the planet, especially the "Penalty to hit" storms and "Lowered Shield Generation". Enough storms lowering the odds to hit could render PDC irrelevent, allowing you to strike at the planet with your missile boats. These ships would need the speed to escape the missiles launched by the planet however, but that might make for a nice softening blow. If you would rather launch a second wave with conventional weaponry, removing the storms should not be so difficult.

The Lowered Shield Generation storms *might* do the trick as well, if they actually negate shield generation from units. I cannot swear it works however, as weapon platform shields are treated as armour for all purposes, but who knows? Lastly, you could get a Crystalline friend, and start fielding those Crystalline Armoured vessels. It *should* work as usual against seekers, and seekers have an usually low damage rate, so that could be fun. Something I will have to try out I guess.

And the standard disclaimer: most of the above post is purely opinion, unless stated otherwise. The day where I will try to take a Proportions homeworld is still far away. Or perhaps not, hmm...