if i may add, i also kind of stopped to use the dutch train set for the loading time reason too, even with the recent reduction...i haven t tried the latest nightly from today though.
i tried many set and to me the one that have the most perfect loading speed (in term of gameplay) is the japanese set with the parameter for the fastest loading speed enabled though.
It s stay simple with, it seems, only two different loading speed for passengers, one for "commuting" and the other are all the same.
Why this is good, is that when you set timetables you can more easily guess (after a few automatic timetabling and a few trial) how many ticks should be enough. i mean it s easier cause once you know the time needed you know it for the rest of your game cause trains only use two different speed, and not something like 20 different speed loading time wich are impossible to use without having to check each time how much this particular train needs. (and i m not talking of the pain when you replace a train with an another and have to redo the timetable entirely...)
Now i m not against, at all, the concept of the dutch set wich make change the loading time depending on the kind and number of doors...but that's way to many possibilities to "play" with right now. i think the system of categorie from japanese set make more sense, i guess a balance between the two is possible. i mean, i think something like 3 or 4 categories would fit already nicely to your concept, and it seems used already for some bus set (ikarus afair). let s imagine something like Metro/Local and régional trains/ emus-dmus /high speed-long distance or Even more simple something like in Ikarus Instant/Fast/Medium/Slow...
now in term of numbers... i usually always reject set that put the maximum loading time (for the slowest loading passenger trains) over 600 ticks (and i mean loading +unloading). the main reason is that i play with timetable so i allready need to put greater waiting time than necessery,especially at terminus or important hub station and with cargodist enabled ( i sometime put until 1200 ticks waiting time manually for a train able to load and unload in 600, only to be sure that my trains are not running late for too many run in a row, wich is necessary when you share tracks).
And on the subject of loading speed of freight trains, i m surprised those tends (in most set i know) to have rather fast loading speed compared to passenger, or the same loading speed...how come no sets make them slower, while they are the kind of trains that stay in station the longest anyway (don t we almost always use full load orders for freight, right ?)
voila, enough said, and that s just my opinion of course, but still, I hope it can help you guys to choose what loading time your (very nice) set could use and please somepeople (well at least me obviously