Yes, I agree.
I've played around with AI a little bit and it's a HUGE tool that can be used to make your world much more alive and get more stuff done. However, once you get into complex operations for me personally then perhaps your route is too big
I was in Run8 for about a decade and despite having MP, the AI worked great and had simple functions. Obey the speed limits, don't crash into other trains, and follow the signals. It had no uncoupling commands. Still Run8 developed plenty of routes in one region that quite frankly needs at least 20 people to operate at prototypical levels.
By all means if you want to spend the time to program the rules you can do pretty much anything. You can even add those pauses in there that the post above mentioned are part of normal operations. In fact I'd go further and say the player and physics (run8 has awesome physics) not to mention walking back to the engine from throwing switches, grabbing an updated switch list takes lots of time.
What follows is my strategy, and only mine and I still haven't fully developed the route yet. In fact I can't operate on it since I switched over to DEM and started from scratch but it's so worth it in my opinion.
1) Run a route or area that you can manage (unless you are using multi-player). I haven't tried MP in Trainz, in Run8 it works awesome but I'm no in Run8 anymore because regions get too big and not everyone is around when you want to run.
2) The route you manage should have a traffic structure that is not too busy or complex. So for example I'm developing Niagara and I'm sure there are several similar regions like mine out there. Personally I don't like switching all the time I do enjoy to just run or watch my railroad work (I think that is what you are after). So I'm developing a region that has 2 class 1's and a short line. Both class 1's CN & CP have limited traffic. CN has commuter service which is easily programmable in comparison. As far as freights go CN has basically 1 mainline feeder train each way a day as it serves Niagara and breaks down into 2 other trains and locals each way at Port Robinson for the United States from Canada. CP on the other hand has smaller trains but perhaps only half a dozen. CN has only a few industries. CP has even less. The shortline has about half a dozen spread out over a greater distance.
3) Run an open ended session - Quick drive if you will, and keep saving it and coming back.
4) Run a 24 hour cycle. Even if the region is quiet at times find a place where there is some traffic perhaps (most of my staging is near busier cities) and have the ambient sounds of cars, traffic lights, sunrise, sunset, weather, etc.
5) Pick and choose the mainline jobs you want to run, or have them drive to locations. You can have them do 1 operation such as a setoff. I believe one of the uncouple commands I have will do that. So you have it run to a spot, perhaps wait so long, uncouple again etc. But as suggested if it's a simple operation it doesn't take much to switch it out so just have it drive in the yard, and message you for your attention. If you can't get to it right away not a big deal, in fact it's prototypical. The crews will be shooting the bull on the ground with the crew change or waiting for a taxi to show up.
Anyways just some ideas. At least that is my plan. I was working this plan a bit before I switched to DEM and started over. Again it was worth every day, week, and now month I've had to recreate what I was doing before even better.
Thanks
Sean