Having followed the thread with great interest I feel a desire to chime in.
For whatever my opinion's worth, the idea I like best is Martyn van Buren's: not nerfing, but separating things up, so the core guard posts and brutal picks also get seeded on the core worlds as well as the homeworlds, with the core worlds being a bit easier than the homeworlds: brutal picks get placed on homeworlds first, and the "regular" guard posts on homeworlds are a bit tougher than the "regular" posts on the core worlds, but brutal picks would never get placed on the same world as another brutal pick unless there was nowhere else for it to go: i.e. three brutal picks in the RNG, one homeworld and one core world, so two brutal picks on the homeworld and one on the core world. Very unlucky, yes, but not as impossible to deal with as it would be with the current system.
This may be more time-consuming than just lowering the ranges of everything, but I think would retain the desirable interest in dealing with the hard counters (blanket tachyon coverage, wrath lance, teuthida (I've never actually had to face a teuthida, the only games they got spawned I ended up losing before I got there anyway...)), but not allowing them to completely overwhelm all options. The planet-wide hard counters are not such a bad thing after all, it's just overwhelming to meet them all on a single planet.
Now, this means that on maps where you're likely to have just one core world for each homeworld it will still be quite tough going, but that is partly a matter of choice on the map type. If you choose a crosshatch map, you've got other problems to deal with, if you've got an X or spokes map, you've likely got fewer other problems to deal with, so your endgame is tougher.
I would personally prefer to retain the mechanic whereby the core guard posts have to be eliminated to attack the AI homeworld command station, so they cannot be bypassed completely, but as they are split up across worlds (at least two, but possibly more depending on the map setup), it's less of a chore trying to take out each one.
Allowing a bit more of the strategic reserve to be deployed in defence of core worlds might not be a bad thing either, particularly with a slightly lower rate of deployment.
The end result is that the core worlds are quite a bit tougher than present with a proportion of the core guardposts, a little more of the strategic reserve assigned to them and a possible single brutal pick, but the homeworlds are significantly easier than at present with much lower odds of multiple brutal picks, at most half the current number of core guardposts (though the "missing" ones are still getting replaced with very high level regular guardposts) and the option for the player to deplete the strategic reserve via the core worlds a bit more than is presently possible.
In game terms, the result is something like having one or more mini-bosses before the final boss, but the final boss itself is easier than it currently is.
Edit: Put another way, you retain the fun of working out a plan, executing it and either succeeding or failing, but massively reduce the !fun! of dealing with near impossible combinations.