You are asking for opinions… well, you will get mine:
I hate rail shooters. With a passion. Played some in the 90’s when they were all the rage, and game devs experimented with all those limited expieriences like interactive Movies and stupid things like that.
It was a boring expierience even then. It was the lowest point of the stupid Die Hard console game for the PS1… the other modes were not that great, but at least you could amass big piles of bodies in the 3rd person stealth Die Hard 1 mode by making a dead end staircase youre mouse trap the goons were walking into one after another, and driving around the Die Hard 3 bomb collecting race mode was slightly fun because of all the mayhem you could cause driving into other cars and pedestrians.
The Die Hard 2 on rails shooter on the other was just boring. No fun to be had straying off the beaten path because, well, the expierience was on rails.
Now, that might be an example for a BAD on rails shooter. And certainly, as always you will find fans that are not so fussed about the limitations of the on rails expierience.
But the on rails shooter died in the 90’s, as far as the AAA games are concerned, for a good reason. Even today some way more interactive shooters are critisized for their “on rails” expierinces where the player is restricted on where to go, and is shuffled from set piece to set piece, with no real agency in how to tackle obstacles or to play the actual game. People start calling that interactive movies.
I would imagine, getting around THAT in a REAL on rails expierience will be even more difficult. Giving the player agency, and different ways to tackle obstacles… difficult without giving the player freedom of movement.
To get back ontopic: my personal, very pessimistic opinion is: I don’t think there is enough of a market to justify the development of a whole “on rails shooter engine”…
It might be that the limited VR equipment of today will create more shortterm demand for on rails shooters… but you can bet these shooters will die a quick death once players tire of them, and technology advances more. It will be the 90’s all over again for these on rail expieriences.
Also, as other have said… how hard is it really to create an on rails expierience? It might be useful for the coding iliterate, everyone who knows his stuff programming wise might have written the code for his on rails expierience in a breeze. As soon as player agency is taken away, testing is a breeze anyway, so coding will be quick, testing easy, and no many iterations needed.
But hey, prove me wrong if you are hellbent on it. Maybe there is enough of a market for on rails shooters, maybe there are enough devs who would pay for such an asset to speed up their devlopment. Good luck with your asset anyway 