The hotkey works just before a building is marked for construction. Pressing it changes the subtype. For example, you can click the icon to build a Lancer tower or hardpoint, but instead of clicking directly on the one you want to build, you can click on the Lancer icon and use the hotkey to specify whether you want to build a tower or a hardpoint. In the case of base structures, like a factory, you can choose what module level to build it to, instead of clicking on the same factory three times, waiting for the truck to finish building the modules.
If someone has the time, a patch can be submitted via ticket to list every single weapon with every single structure option, within reason of course. No Howitzer Hardpoints, but Pits maybe to go along with emplacements to add a bit of aesthetic and possibly strategic variation. Like Pits can have a bit more HP or armor to help with CB attacks, but will cost more and take longer to build. And possibly Heavy Machinegun Emplacements to go with bunkers as a cheap and easy to build alternative, along with the tower and hardpoint.
As for research, yes keep the current requirements in place, but once they're researched, they can be added to the variants available for construction when using the hotkey. The hotkey itself should be easy to remember and easy to use. I'd even settle for the left and right arrow keys.
This will also hopefully (at least for now) appease the players who want to see a Structure Design button as part of the UI (and I'm one of those people
Really, the only difficulty I foresee here is the design of a new hotkey. The rest is basic stuff, if a bit time consuming for the structure templates. I'd love to see this on a Master Build.
Also, don't hesitate to improve this idea by pointing out any problems or flaws in it


