For players' reference, I thought that it might be helpful briefly to list some features present in Standard that, for various reasons, are not supported (or work only partially) in Experimental. They are as follows:
(1) AI players;
(2) scenario scripting (the Squirrel API);
(3) the GUI theming (this isnow partly supported);
(4) the new "just in time" ("JIT 2") industry supply system; and
(5) the "no routing over overcrowded" option.
(4) and (5) are not supported because they are not consistent with the way in which Extended works. There may be other features in this category not listed here.
(1), (2) and (3) are of more significance: these are not supported because I cannot afford the time necessary to integrate these features with the way in which Simutrans-Extended works (I could in theory do these things, but it would take a very long time, and there is a very large list of things of much higher priority). The code (1) and (2) is still present, but is often not fully updated and does work properly or at all.
None of this second category of missing features is something that I consider to be of high priority (the main focus of my development of Experimental being large online games, to which AI and scenario scripting is not relevant), although the GUI themes are of medium priority (and there is now a partial implementation of these).
It would be splendid if anyone were interested in integrating these things properly into Simutrans-Extended. The scenario scripting and GUI themes are likely to be worthwhile, but I have doubts that any workable AI that can interact with all of the Simutrans-Extended parameters in a useful way could be crafted in anything approaching a reasonable time (although if any extremely skilled and dedicated programmer would like to give it a try, I shall not stand in her/his way).
Edit: Modified the above post to refer to the new name of "Simutrans-Extended".