What do you think the reaction of the other Clans would be if the Wolves-in-Exile or the Nova Cats were brought in during the Jihad, managed to conquer Terra away from the Word of Blake, and then declared themselves ilClan?
Well, I would imagine
both would put the other Clan in 'hot water'- especially if it was the Exiles. Both Clans are still viewed with suspicion and distrust by their...erm..hosts.
If one of the two was to suddenly take Terra (from WoB, RotS, Wolverines, Aliens whatever)
and made a claim to ilClan...leader of the Clans.
Well, Warden intention or not, I would think many people who were suspicious would be proven 'correct' by the sudden turn.
And if one of the pet Clans can go rabid...so can the other.
That's how the Inner Sphere would react, I'd imagine.
As for the rest of the Clans?
The Council of Six wouldn't acknowledge it. As they said in 'Wars of Reaving' when the Sharks brought them up- they're 'not Clan'.
And the Homeworlds? Much the same I'd imagine.
In other words, the Nova Cats and the Exiles might acknowledge the other's ilClanship, but they'd be the only ones...and they would lose friends and make enemies for nothing.