The "cannot reach" warning doesn't actually prevent building and appears for the first built item since last entering map view. I get it whenever switching between normal and map view to make small changes (or building out of physical range in normal view). The warning can be prevented in map view with Ghost Mode (https://mods.factorio.com/mod/ghost-mode) bound to the same key as Toggle World Map.

There doesn't seem to be any combination of existing mods that 1-tick pulses a CC remotely:
Pushbutton won't support remote interaction: https://mods.factorio.com/mod/pushbutton/discussion/5f417bec3437882cc217fe4d
This doesn't work on Pushbutton, only vanilla CCs: https://mods.factorio.com/mod/lo-remote-constant
These add new entities that don't pulse (basically reskinned CCs): https://mods.factorio.com/mod/remote-switch; https://mods.factorio.com/mod/Switch_Button-1_0
This works on Pushbutton but "respects player reach": https://mods.factorio.com/mod/combinator-toggle/discussion/60f6845891a7f3f7b0976227
Other solutions: An edge detector + decider can interpret both On and Off (aka =/0) as "pressed". Rising/falling variants feel clunky to setup repeatedly for editing many memory cells. Long reach mods feel like overkill for pushing a button between physical and visual range.