TL;DR
Tanks and Car's can be controlled like spidertrons remotely and auto fireWhat ?
Tank's and Car's can be controlled with the same device spidertrons are controlled with, they also will auto fire the cannon and machine guns.Mod's have been unable to create it due to the limitation of the entity and no desire to remake it as a "spidertron heavily modified".
This could be achieved by overhauling tanks and cars to have similar API interfaces with the spidertron allowing mods to enable the feature if not suitable for main game so players can opt in the for the functionality easily.
These changes may mean that limiting vehicle slots like chests would be useful to allow inserters to fill vehicles up.
Why ?
When playing on a deathworld or anything with the rampant mod, before getting to spidertron's you find the car immediately useless and the tank only useful if gotten very fast and early to do a land grab and then turtle and turret creep until spidertrons. If you do not greatly reduce evolution rate by the time the vehicles are unlocked they are already useless. This means only turret creeping is viable way to expand which is limiting. The proposal to allow tanks / cars to be remote controlled with automatically firing weapons allows the player to decide if they prefer to turret creep or need to manually setup / maintain a group of vehicles to fight the biters. They will also double as a defensive force should the outer permiter of a base be overwhelmed they give the player an option to defend with a mobile force pre spidertron. The spidertron which fires missles only is also very limiting when needing to use different ammo types to hit weaknesses on modified biters so this allows players to mix "guns, shells, missles" which can lead to RTS level play where you have tanks shielding spidertrons firing over the top of them.Outside of pure combat this would also allow a pre train resupply vehicle to outposts to be easily manually directed to move between two points with inserts.
It will also allow early game transportation across long distances to be "click" and afk to avoid needing to drive everywhere.
References
RoboTank:This mod makes a new entity that will maintain its offset from the players vehicle so a group can go into combat and demonstrates the kind of value the tank can have when they can be used in groups rather than solo to demonstrate its usefulness and potential fun to the game as an alternative to turret creeping.
https://www.youtube.com/watch?v=M64LyVkl6Ac
The below two video's highlight the current kind of meta in factorio pre spidertron which only allows 1 single way to expand viably when surrounded by lots of enemies which is to tower creep your way to the next resource.
Vanilla deathworld turret creeping:
https://youtu.be/WDGV0nsQP8s?si=0YL9Lk9yU9-KWqi4&t=775
Rampant turret creeping:
https://youtu.be/FLbJMBM7QnM?si=XoeFSkH9Sh0OfgKX&t=1598