Hey,

these are actually a number of ideas, which are connected in a way.

First of all the introduction of starting numbers. What I have in mind is an option similar to the current numberplates. You can type an up to 3 digit long number. This number is shown next to the racer's name in the connection message, connection list, the live running order list and the results list, if the server is set to /league=yes.
The /league command shall have the options "yes", "no", "endurance". "Yes" also restricts the ability to join the track to drivers with different starting numbers. It also locks a starting number to a certain driver. "endurance" does not lock it to someone specific. What "yes" and "endurance" have in common is that laps won't reset to zero if you shift-s and rejoin. In "endurance" it also continues the lap counting of drivers with the same starting number.
I realise Shift-P seems to be a problem, as changing setups during race or qualifying sessions should not be supported, when it is set to "yes" or "endurance".

Then the thing with the window number: That would just be an visual thing. We already have something similar in the GTRs and NGTs where the number plate is visualized in the side mirrors. Instead of the numberplates the starting numbers could displayed in the windows, in the rear window on the driver's side, in the front window on the alternate side. In the side windows it is also displayed, together with the in-game driver name.
That could be activated and deactivated serverside with /windownumber and /windowname for all cars (except single seaters obviously)

For endurance lap counting, it can be done with InSim and some leagues are already doing it. I'm not sure if there's any problem with that approach. More connection load?

For the window display on single seaters, the number/name can be placed somewhere on the sides of the car, so no difference here.

Quote from Keling :

For endurance lap counting, it can be done with InSim and some leagues are already doing it. I'm not sure if there's any problem with that approach. More connection load?

The problem is that drivers actually don't know where they are,get shown blue flags from cars who are actually lap[s] down (since you are starting the lap count again from reconnecting). All this is suggested to make league admins' life/job easier and drivers race more clear.

Quote from Keling :

For endurance lap counting, it can be done with InSim and some leagues are already doing it. I'm not sure if there's any problem with that approach. More connection load?

Quote from Eclipsed :

The problem is that drivers actually don't know where they are,get shown blue flags from cars who are actually lap[s] down (since you are starting the lap count again from reconnecting). All this is suggested to make league admins' life/job easier and drivers race more clear.

Yeah, additionally LFS is gifted with quiet a number of endurance leagues. An internal support would be a nice addition to the product since that would help that kind of league racing and league racing as a whole a lot as timeouts/lost connections would no longer end one's race or the race of a team.

Quote from Keling :

For the window display on single seaters, the number/name can be placed somewhere on the sides of the car, so no difference here.

Well those are skinable areas so this can be solved using sinks.

Problems with endurance races can be easily fixed. We need something at server-side to block all flags and other HUD info. Then we can handle everything with InSim. Let's say "/nohud=yes" in server config.

Why everyone wants to do it with 3rd party aplications? Would be much easier to have native support for that...

Quote from misiek08 :

Problems with endurance races can be easily fixed. We need something at server-side to block all flags and other HUD info. Then we can handle everything with InSim. Let's say "/nohud=yes" in server config.

Then you again have to set up something. My suggestion seeks for a native support of endurance races, sothat you do not need 1000 things to run longer races

Would be much better to have it nativly supported