The problem with that @Exselsior is that you can't just queue up multiple walled PD with one set of orders, you would have to start your PDs and then do more clicks when it finished to queue up the walls. And if you wanted to make multiple PDs your engineers wouldn't start making walls until all of the turrets were done, unless you babysat them. So it would actually cost more APM and it would promote bad habits.
And we can't make point defense default to having walls around it (default to using a template instead of a singular build order) because people don't always want walls around their PD, for example if they're making teleport defense.
One solution is just to make PD higher so it doesn't benefit from walls, and give it a corresponding HP boost. Then find some other way to make walls relevant in the game as walls -- not just relevant as extra armor for t1 PD. It wouldn't ruin the game--you would still suffer if you spammed PD too closely together because splash damage would damage multiple turrets at once.
Maybe walls just shouldn't block any shots at all. That would be better than having them block shots from some units but not others (because if we raise t1 PD height, some units are low enough to the ground that maybe vanilla walls would still block their shots depending on terrain elevation). Walls would still be able to block units from moving forward.
We could also find a way to nerf the ability of engineers to quickly reclaim the walls without making the walls take longer to build. If it took 5x as long for engineers to reclaim walls, it would be harder to just send an engineer to the front to make a hole in the line and more painful to use your ACU to open a hole (but still very doable).
This would make the game less complicated. I'm not seeing a downside.