The issues with premade coasters is licensing, Frontier can't just pick the smiler and put it into the game. They need a license for that and then it gets complicated, lawyers get involved and everything.
Who pays whom?
Frontier is basically giving parks free advertisment for their IPs, parks probably argue: hey our IP is boosting your sales and so on. So stuff gets complicated real fast, probably the eu will also have to look into it, since it could be seen as a form of product placement, etc.
So yes, while there was always some kind cooperation between Frontier and serveral companies (Hershey, Six Flags and Cedar Fair, which is now also six flags) it is not that easy and gotten way harder over time.
Especially since most of those cooperations would be exclusive. If you go with merlin, you basically block compagnie de alpes (walibi), plopsa, and the major independent parks (Efteling, Europa Park, Phantasialand) out, maybe they want to cooperate with DLC IPs again and since Amuesment Parks and Movie IPs are most of the time (partially) the same shareholders there could also be trouble on that front.
So short answer, it is not that easy