Find your sponsors, tell them you need to sign him on a long term deal for 5M a year yesterday.
If Seixas still won't negotiate, bench him for the remainder of his contract.
Decathlon has some pretty capable riders to help Seixas with whatever goals, single day stuff and GC goals, if Ineos is flush they could chose to ditch a couple of older riders. Teams can go with UAE model with no designated sprinters and no dedicated riders for a leadout train, bunch of other threads saying something about UAE not having anyone in the top sprint positions, they want it that way.
I think that Decathlon is a great place for him to land..I don't know about sales or their products but I can't help but think that Van Rysel is selling more product. It just looks like a winning situation for everybody.