anni defenetly has a point here.
still walls to prevent terraforming sounds not bad. only thing that comes to my mind is that ppl will use it to build castels that can not be entered with terraforming.
there has to be a good benefit for the defenders, but making it too big may cause some serious issues.
terraform a wall. place wall segemnts behind it. if one tile around can not be terraformed then you will not be able to destroy that wall segments from outside. even if you implement terraforming slope limitations it still will be hard.
i still prefer the terraforming inhibitor aura buildings that were annouced some time ago. these will slow attackers to tear down your terraforming and also would slow just to build a a ramp. and go over it. same goes for just terraforming some cover to block enemy bot and turret fire. of cource the aura needs to have a real big radius or it will suck deeply.
the good old question that you always need to keep in mind:
if you give players a toy, they will not use it like a tool, in the way it is ment to use. they will abuse it to the max. they will always drive it to the max. and with that you need to add savety limitations so that this will be prevented (see walls to the sky. normal ground would just collapse if build that high and thin).
would DWU block terraforming help? yes. will it give ppl even more ways to exploit? yes!
one other thing that i want to bring to discussion here: with the current terraforming options you might not be able to rebuild your defensive terraforming after a attack to its former glory without deconstructing your buildings. you can mess up a nice plan so that it can only be rebuild with beacons. if oyu still have buildings around then you have a problem because manual terraforming will not bring back the nice original state. atm you can only deconstruct if its worth for you.
i think here is also a solution nessessary. one solution that i came up is a MPC building taht can terraform from a selected plan. in a large radius. but it will do that very slowly and only on ground were no players are around.
of cource this would also need that terraforming would acualy follow the terraforming plans to the end and not stop before completion as it does often atm.