Well umm, you can either make a huge region that will cover your entire map and another small region which will be outside the huge region. You can also make that if a hero respawns by accident in the not-supposed-to-respawn region, you can move it back to the huge region. Like throwing a guy off a bus XD
Ok seriously, make two regions, one to cover where you want units to respawn and other where you don't want em to. If they interlace with one another, then you'd have to think of something other than regions for the trigger. If they don't then the trigger is easy.
For this to be done easily in GUI, you will need a few Custom Scripts, but only for the loop that is required.
Here's a version which uses only locations, so it'll be slower than the next version.
Here you have to create a location even if you're not gonna use it, which is quite a waste
Trigger:
Respawn at Random not Region
Events
Unit - A unit Dies
Conditions
Actions
Custom script: loop
Set Spawn_Loc = (Random point in (Playable map area))
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
(Block Region 1 <gen> contains Spawn_Loc) Not equal to True
Then - Actions
Unit - Create 1 Footman for Player 1 (Red) at Spawn_Loc facing Default building facing degrees
Custom script: return
Else - Actions
Custom script: call RemoveLocation(udg_Spawn_Loc)
Custom script: endloop
Here comes the more complex version, which uses reals at first instead, so you only create a location if you're gonna use it, which seems and is more efficient
Trigger:
Respawn at Random not Region
Events
Unit - A unit Dies
Conditions
Actions
Custom script: loop
Set Spawn_X = (Random real number between (Min X of (Playable map area)) and (Max X of (Playable map area)))
Set Spawn_Y = (Random real number between (Min Y of (Playable map area)) and (Max Y of (Playable map area)))
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
Or - Any (Conditions) are true
Conditions
Spawn_X Greater than (Max X of Block Region 1 <gen>)
Spawn_X Less than (Min X of Block Region 1 <gen>)
Or - Any (Conditions) are true
Conditions
Spawn_Y Greater than (Max Y of Block Region 1 <gen>)
Spawn_Y Less than (Min Y of Block Region 1 <gen>)
Then - Actions
Set Spawn_Loc = (Point(Spawn_X, Spawn_Y))
Unit - Create 1 Footman for Player 1 (Red) at Spawn_Loc facing Default building facing degrees
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.