Variable Session, How Would You Like It?

The question arises as I am working on a session that might play out in three different ways. This will be done based on a trigger three quarters of the way through the game, which would be time dependant. So if you perform that part at an average speed/time period, the game would finish after one more shunt. I should point out it's a shunting session. However, I was thinking, if you reached that (hidden) trigger early, instead of the last shunt, you would get a different one that would take a little longer and give a few extra points. I'm trying to think of what would make an interesting third option like, if you are incredibly slow you will get something else. Can't do a slap on the wrist due to (eck) social distancing (please practice...) so are there any suggestions?

As I can't add an extra long shunt as the object would be to NOT get extra points, maybe it would end at that afore said trigger, ie abruptly? Suggestions very much appreciated.

Probably more complicated, but how would a story book scenario go - example:
do the first task and then pick from a 2nd, 3rd or even 4th new tasks.
This leads the player off in a different direction each time.

I was a little miffed the first time I successfully ran Fossil Fuels just to be downgraded and told I could have run it faster. Is that real world? I realize trains have to run on time, but I thought I had done a very good job. I eventually ran it over again faster and got the full score but I still wonder. Especially since that is Kickstarter and the speed limits jump up and down every minute so it is hard to keep a consist going consistently - as it were.

I would like to see a session where a player can rerail the locomotives and rolling stock after a derailment or accident with an operating crane and other recovery equipment like front end loaders or bulldozers. A recovery depot with equipment will be nice where we can make up our own train and enter a section with permission from operating or yard masters . Another idea I have but can't do it myself is to be able , for example , to uncouple certain strategic vehicles which are derailed to set them aside with helper loco's or similar, to clear the section so service may continue.
I realise the challenge and monster amount of work that will be involved in such a session operation and equipment for trainzers who can build such assets but do you guys think it would be possible to do such moves in future ?

Well, interesting ideas, although the last is totally impossible. However I'll refrain from slapping the slow driver over the wrist, I'm thinking along the lines of what butler57 said. 1) Not bad, basic session with a possible say 600 score. 2) Well that's rather efficient add an extra shunt and say a possible 800 score, and 3) Wow, that's super fast, extend the session further and a possible 1000 score, and possibly even further.

This is going to get complicated (for me) but should work out interesting for the player when I'm done. Thanks for the thoughts.