LogFAQs > #880517618

Possession - A possessed merc's leader cannot roster them or use any of their abilities. [...] Any abilities that were sent at the possessed merc before the possession will still resolve even if that shouldn't normally happen due to team membership.

Doesn't look like it cancels (and I don't see anything special in Shanoa/Grigori's abilities either). So yeah, I think you're right.
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You put your RESOLVE HAT back on, which conveniently is the same hat as your NORMAL HAT.
{Drakeryn}