I'd like to share what I've been working on today: the first beta of version 7
Most importanty it has some support for NewGRF trainsets. I have tested it with URKS, UKRS2, NARS and 2CC. FIRS and ECS are supported, although the AI may have a very hard time if only trains are enabled, as the running costs of these sets are quite high. So the AI only does decently if road vehicles are also enabled, but on easy difficulty it succeeds with trains only as well.
Engine selection is made in a way that if the default train set is used, the AI makes the same choices as the previous versions. My biggest challenges were articulated wagons and express trains. Articulated wagons (like the 3x Freightliner container rake in UKRS) tend to be very long, so I tried to exclude them, but in UKRS2 and 2CC all wagons are articulated for some reason, so I cannot make a distinction. So I introduced blacklisting for wagons, and extra long wagons are put into the blacklist. (I cannot determine their length before buying one...)
Some engines cannot attach certain wagons, and this was also quite a challenge for me, again it was solved by blacklisting.
There is some minimal support for extra railtypes, so the AI won't try to build maglev all the time when there is only a passenger train available on maglev.
Range limited planes should be also supported, but I encountered some strange behaviour, I opened a topic about it. Most probaby I don't know something
And of course I fixed the bug Poppis reported above.
So the new version is available in the first post, please give it some time and test it
It's been quite a time I last worked on this AI, so it will need some thorough testing before I release version 7.