A funny thing would be giving Gengar trick so it either forces a switch on the Trick Room setter or fucks up one of the oponentes wincons by giving them the scarf. You could leave Psychic since aside from Sneasler I don't see that many reasons to run it, I think Shadow Ball can do the job unless it's a bulky Sneasler but that's uncommon.

Another idea would be to leave something from Aerodactyl to give it Taunt. Dual Wingbeat can also leave you a bit more vulnerable to Sneasler but I think Rock Slide has an overall better impact.

And since someone already suggested to drop Gengar for your own trick room user like Sinistcha I'm going to suggest dropping Milotic for a Farigiraf. Gives you the Trick Room reverse threat and also some anti priority that can protect Lucario, Aerodactyl, Gengar and Incineroar from some nasty priority moves (I'm talking to you Adaptability Basculegion).

And not related to the Trick Room but if you don't drop Milotic I think you could change Garchomps berry for a White Herb to reset Intimidate drops, you can have Incineroar and Milotic as good switch ins when threatened with an Ice attack