An issue i run into a lot when playing is how there is no good way to clear. If with a full AAI setup it requires either a crazy amount a circuits to automate or constant manual adjustments.

Methods to help simplifies clearing.

1. "clearing radar" - This is an object that once place all cave walls in either a radius or chunk get marked for deconstruction and any new walls that appear get mark soon or immediately.
2. Custom AAI "path" block that once placed lets you edit it for things like "radius", "start point", "path id", and "vehicle type". Once the settings are set you click "build path". It then creates a zigzag path for clearing an area. If a hauler is set instead of a miner, it needs also the "miner" vehicle id as well as a "base path" id for it to mimic and then it increments the path in order to ensure the hauler reaches the miner without getting in its way.
3. Bore vehicle - Similar to the miner except; it does not collect stone and voids it, it can not mine ores, only works in the underground, is way faster than the miner, consumes fuel faster, produces way more pollution, larger dig radius, and an increase chance for collapses to occur. Could also optionally have a ammo type called "drill head" that degrades with use.

Nice ideas! Especially the 1st one. Why didn't I think about something like this...
Could be a nice thing with recursive blueprints. Could also mark itself for deconstruction if there are no walls left in the covered area

Thank you! yea i was thinking that as well. For the other two it was sorta a "lets try to give setups for earlier, mid, and late game" Since 1 is only really g0od when you have roboports its most ideal for late game, 2 is good for early game miners or late game stone collection, and 3 is good for mid-game when you just want to clear large areas or long corridors without having to constantly deal with inventory but don't quite have the bot network to support using bots to automate clearing.

mid game stone collection*

After testing a bit with AAI vehicles, I think I can break down no. 2 to something else. You can easily command a miner to dig a straight tunnel in a direction, and for area clearing, I could add a special zone type that disappears when that tile is cleared. No crazy circuits needed.

Another alternative for no. 1 could be a modified deconstruction planner, that "remembers" where used and all new walls are marked for deconstruction

Would it be possible for number 1 to make the void tiles be mark-able, and that any new wall that spawn on them get auto-decontructed? Might need a new tool for that though.

That was my idea, and I think I can make the deconstruction planner able to do that

Could you make the deconstruction planner limit to be within rand of a roboport be either a toggle or have compatibility with mods that add in non-roboport based helpers? Such as these two mods? Also does this effect personal roboports?

https://mods.factorio.com/mod/companion-drones-mjlfix
https://mods.factorio.com/mod/spiderbots

oh and i almost forgot nanobots
https://mods.factorio.com/mod/nanobots-refined

The Restriction will be removed in the next release

For No. 3 I have two different ideas:
- a rail-bound thing like already suggested in https://mods.factorio.com/mod/Subsurface/discussion/682b5055824b887c1e5204ef
- a borer vehicle you suggested, with the addition that it places transport belts behind it to evacuate excess stone

only thing is that they only dig straight

The biggest issue i could see with the railbound vehicle mentioned is the same issue with miners and that is storage with the added issue of needed to also supply tracks. As once the wagons are full it would have 1 of 2 options. The first being it stops the second be it keeps going spilling up to infinite items on the ground. If it ran out of tracks it could only stop. To make this feasible you would want to do 2 things. Make a never ending stop. Pretty much the bore head of the train would always have a stop called like "tunnel" that would always be just out of reach. The other thing you would need is either the ability to monitor cargo contents via circuits and/or custom cargo containers. (the the circuit thing is not already something doable in vanilla)

What i would recommend for the last items is circuit based stuff. For compatibility make a building or circuit that lets you monitor trains cargo amounts remotely. This is so you dont need to make custom cargo containers for every modded container.

This would combine in the train of you choice trying to go to "tunnel" then you could have a circuit condition for when the cargo is full to toggle "drop off" station and toggle "tunnel". This would let you empty the train and refill the rails and such. For more flexibility and less endless digging, you could have it also able to have the "tunnel" station, be optionally a set point.

With the other vehicle this is a nice idea, but the logistical issue i see is supplying the belts. Since vehicles will have a hard to driving on the placed belt making it harder to navigate. Could get around this with the belts being placed on the side with an addition belt "feeding" the vehicle, so you could autofeed it belts.

For all cases of inventory full/not enough resupply, I think the best is to stop the vehicle, whatever it is. The Rail-bound thing could be set to go back the track to an unload/resupply stop. There are also more options as you can add more cargo wagons for more inventory size.

The wheeled thing can only stop as I don't see it turning and going back.
I could also modify the aai miner to work with supply and evacuation belts

For the miner i think its fine to just improve how it already functions. AAI vehicles has a lot of customizability to work with. The idea of the bore is to make handling the storage items easier. Since miners can't move to unload their contents this is a struggle but rewards player who work haulers into their system.

Ideally the bore would just delete the stone it gathered as to not have to handle it at all, but it is also a part of the struggle managing inventory. So The belt solution lets that be a struggle while also making it far easier to drill tunnels. The belt input i mentioned was so players could to a degree automate it so it could keep going for farther away outposts for worlds such as rail worlds to be feasible. Since you would need thousands if not tens of thousands of belts to go that far.

All that matter for the trains is that they can empty cargo and resupply. Due to how much stone you get while digging be very large 4 cargo wagons of vanilla size could be filled pretty fast.

Me personally what i started doing when digging is just making landfill or that tunnel fill you added. I usually have to empty after i get over 1 or 2 thousand landfill though.