Hi,

just wanted to give you a rough idea of what to expect. Of course nothing is set in stone :) I will try to keep the post updated. The list is roughly the order i will take a look at, unless i change my mind ^^

Idea - how likely i can/will do it - when
Better endgame (mk1/mk3 entrances?) - maybe - with recent changes i think it is less of an issue nowadays
no walls option - likely - eventually
darker caves - maybe - will try it soon but could be tricky
less chaotic caves (bigger halways and areas, configurations) - difficult - not sure
better entrance graphics - maybe - eventually
water generation in caves - difficult - not sure
full AAI pathfinding support - maybe - not any time soon
better cave graphics - maybe - probably postponed till factorio 0.16 (see fff-199 tile transition)

please - less chaotic fast! I can barely move inside the cave system. Can't you simply adjust the parameters for the underlying noise?
Also I think you should slightly increase the frequency of all ores. And please move the incompatibility marker for RSO at the top, cause its a very popular mod, I was confused until I read through the text finding it noted somewhere down.
for brightness - look at doc's portal research mod, it contains a lot of helpful code ;)

currently basically i am using random data and then smooth it into a cave. Tweaking the data as far as i tested lead mostly to unplayable caves...
I think rather than the complete random process that is currently used, it would be better to generate hallways and open areas seperately, but it would be a quite complicated change so i am not sure if it can be done.

For the frequency, maybe i could increase it by one setting level per default

i moved the note about RSO to the top, hopefully it is more visible now.
Thanks for pointing out the portal research mod, it seems quite interesting :)

An idea for an end-game(ish) entrance is a Mine Shaft, just a 2x2 belt only (no player travel) entrance, maybe based on the underground belt graphic but larger, craft with several underground (red?) belts and 1 mine-entrance. I really want a 2x2 "shaft" for putting in between 2 rails for more compact train stations without belt weaving, so I might start work on a patch this weekend.