IMTU
Ihatei invasions seem to be to be less of a military incursion, and more of a cross between settlers and illegal immigrants. Maybe like Vikings,they would settle, raid, conquer, or just get killed off depending on how the odds stack up in whatever place they end up landing in, on local attitudes towards them and on whether opportunities come up (such as military service in exchange for citizenship). Their clans might lend some support to them which could be logicistical, military or diplomatic but probably aren't fully committed to backing them, and sometimes really don't care at all: also if they do something inconvenient or embarrassing for the clan, the clan can just disown them. If they were committed to help them, it would be a full scale invasion instead of
Ihatei incursions. Over time, though, despite lots of setbacks and failures, they would build up settlements on underpopulated worlds, colonize uncolonized regions, or integrate themselves into the societies where they emigrate to, expanding the range of Aslan settlement gradually, but generally more quickly than most other races, and possibly retaining and expanding their clans' influence - if they retain those links (which they don't always do).
IMTU, the PCs took the DNR close to and then secretly through Hierate space, and encountered a lot of Imperial spying and monitoring of the Aslan on its way through the Trojan Reaches, and backing of the Storm Knights with secret weapons transfers because of concerns that the Aslan might take advantage of the coming war with the Zhodani to make territorial gains. Also the Muirimi Regency has been on a genocidal campaign against the
Ihatei in the
Iphigenaia and Theron Sectors to prevent themselves from being overwhelmed, and the DNR found signs of this. The Aslan still manage to start up new colonies from time to time, so this is probably a battle the Muirimi will eventually lose.
Looking at Traveller Map, the Aslan enclave near the Trojan Reach has a lot of hi-pop, hi-ish tech worlds, so probably has the industry to really make problems for the Imperium if the clans were to unite and go to war with the Imperium. They could probably swing things for the Zhodani, if they were allies. But that seems to be a different idea to the
Ihatei concept - IMTU
Ihatei could cause the tensions that lead to war between the Imperium and Hierate, which would cause both the Imperium and the Hierate trouble, but they won't be more than annoying policy issue for either side on their own.