So the three possible (and non-mutually exclusive) reasons Clan Space planets suck are:
(1) they are resource-poor
(2) they are unsuitable for human habitation
(3) they are underdeveloped thanks to the Clans fighting one another
The first two reasons make little sense to me, at least without the third reason to contextualize them. I would guess Clan Space is not particularly bereft of resources, just that the resources available may not be easily accessible to governing structures devoted so narrowly to militarism and constantly distracted by armed conflict. Similarly, worlds that are at all suitable for human habitation can be terraformed to be even more suitable, if the social structures in place see that as a worthwhile and affordable goal.
In other words, Clan Space is probably fine and it is the Clans themselves which have been the limiting factor. But who better to redress that problem than the most pragmatically-minded Clan of all? Under the leadership of CSA, the HWC could well enter a new golden age where limited conflict among the surviving Clans allows more room for creating and leveraging social structures necessary to make the most of Clan Space.
And what would wealthy, bored HWCs eventually turn their attention toward?
...