Create an ability based on devotion aura.
Give it a custom model with the protoss blue aura, basicly a gigantic blue circle.
Create a pylon building and give it the devotion aura ability.
Create an attachment ability called DISABLED BUILDING EFFECT and add some fancy effect.
Add some protoss buildings to a worker.
1.
Go to the trigger editor, create a trigger with the event "a unit starts constructing a building"
Check if there is a pylon nearby the constructing building, if not, order the worker to cancel the building and displaya message.
2.
Create a different trigger.
Use the event "A unit dies", set the condition to "unit type of triggering unit == pylon"
set tempGroup = buildings owned by owner of triggering unit in range of the pylon.
For each of the buildings, check if they have the pylon buff, if not, pause the building and add the DISABLED BUILDING EFFECT ability to the building.
3. Create a new trigger, check if a pylon finishes constructing, check how many buildings are nearby, unpause those buildings and remove the DISABLED BUILDING EFFECT ability from it.