There we go, rebuilding works right now. Also has a slightly bugged verb that demonstrates how the rebuilding works, but you need to somehow prevent a zone from updating for it to show more than one "id"

code/ZAS/Debug.dm

@@ -131,3 +131,82 @@ zone/proc/DebugDisplay(client/client)
 			var/turf/zloc = pick(Z.contents)
 			client << "\red Illegal air datum shared by: [zloc.loc.name]"
 
+
+client/proc/TestZASRebuild()
+//	var/turf/turf = get_turf(mob)
+	var/zone/current_zone = mob.loc:zone
+	if(!current_zone)
+		src << "There is no zone there!"
+		return
+
+	var/list/current_adjacents = list()
+	var/list/overlays = list()
+	var/adjacent_id
+	var/lowest_id
+
+	var/list/identical_ids = list()
+	var/list/turfs = current_zone.contents.Copy()
+	var/current_identifier = 1
+
+	src << "[turfs[1]] = [turfs[turfs[1]]]"
+
+	for(var/turf/simulated/current in turfs)
+		lowest_id = null
+		current_adjacents = list()
+
+		for(var/direction in cardinal)
+			if( !(current.air_check_directions & direction))
+				continue
+			var/turf/simulated/adjacent = get_step(current, direction)
+			if(turfs.Find(adjacent))
+				current_adjacents += adjacent
+				adjacent_id = turfs[adjacent]
+
+				if(adjacent_id && (!lowest_id || adjacent_id < lowest_id))
+					lowest_id = adjacent_id
+
+		if(!lowest_id)
+			lowest_id = current_identifier++
+			identical_ids += lowest_id
+			overlays += image('icons/misc/debug_rebuild.dmi',, "[lowest_id]")
+
+		for(var/turf/simulated/adjacent in current_adjacents)
+			adjacent_id = turfs[adjacent]
+			if(adjacent_id != lowest_id)
+				if(adjacent_id)
+					adjacent.overlays -= overlays[adjacent_id]
+					identical_ids[adjacent_id] = lowest_id
+
+				turfs[adjacent] = lowest_id
+				adjacent.overlays += overlays[lowest_id]
+
+				sleep(5)
+
+		turfs[current] = lowest_id
+		current.overlays += overlays[lowest_id]
+		sleep(5)
+
+	var/list/final_arrangement = list()
+
+	for(var/turf/simulated/current in turfs)
+		current_identifier = identical_ids[turfs[current]]
+		current.overlays -= overlays[turfs[current]]
+		current.overlays += overlays[current_identifier]
+		sleep(5)
+
+		if( current_identifier > final_arrangement.len )
+			final_arrangement.len = current_identifier
+			final_arrangement[current_identifier] = list(current)
+
+		else
+			final_arrangement[current_identifier] += current
+
+	//lazy but fast
+	final_arrangement.Remove(null)
+
+	src << final_arrangement.len
+
+	for(var/turf/current in turfs)
+		current.overlays -= overlays
+
+	return final_arrangement

code/ZAS/Functions.dm

@@ -157,7 +157,7 @@ proc/ZConnect(turf/simulated/A,turf/simulated/B)
 	if(!A.zone || !B.zone) return
 	if(A.zone == B.zone) return
 
-	if(A.CanPass(null, B, 0, 0) && A.zone.air.compare(B.zone.air))
+	if(A.CanPass(null, B, 1.5, 1) && A.zone.air.compare(B.zone.air))
 		return ZMerge(A.zone,B.zone)
 
 	//Ensure the connection isn't already made.

code/ZAS/ZAS_Zones.dm

@@ -497,22 +497,22 @@ zone/proc/Rebuild()
 //Implements a two-pass connected component labeling algorithm to determine if the zone is, in fact, split.
 
 /zone/proc/IsolateContents()
-	var/turf/simulated/current
-	var/turf/simulated/adjacent
 	var/list/current_adjacents = list()
 	var/adjacent_id
 	var/lowest_id
 
 	var/list/identical_ids = list()
-	var/turfs = contents.Copy()
+	var/list/turfs = contents.Copy()
 	var/current_identifier = 1
 
-	for(current in turfs)
+	for(var/turf/simulated/current in turfs)
 		lowest_id = null
 		current_adjacents = list()
 
-		for(var/direction in current.air_check_directions)
+		for(var/direction in cardinal)
-			adjacent = get_step(current, direction)
+			if( !(current.air_check_directions & direction))
+				continue
+			var/turf/simulated/adjacent = get_step(current, direction)
 			if(adjacent in turfs)
 				current_adjacents += adjacent
 				adjacent_id = turfs[adjacent]
@@ -522,21 +522,19 @@ zone/proc/Rebuild()
 
 		if(!lowest_id)
 			lowest_id = current_identifier++
+			identical_ids += lowest_id
 
-		for(adjacent in current_adjacents)
+		for(var/turf/simulated/adjacent in current_adjacents)
 			adjacent_id = turfs[adjacent]
+			if(adjacent_id != lowest_id)
 				if(adjacent_id)
-				if(identical_ids.len < adjacent_id)
-					identical_ids.len = adjacent_id
-
 					identical_ids[adjacent_id] = lowest_id
-
 				turfs[adjacent] = lowest_id
 		turfs[current] = lowest_id
 
 	var/list/final_arrangement = list()
 
-	for(current in turfs)
+	for(var/turf/simulated/current in turfs)
 		current_identifier = identical_ids[turfs[current]]
 
 		if( current_identifier > final_arrangement.len )

code/modules/admin/verbs/mapping.dm

@@ -162,6 +162,7 @@ var/intercom_range_display_status = 0
 	src.verbs += /client/proc/Zone_Info
 	src.verbs += /client/proc/Test_ZAS_Connection
 	src.verbs += /client/proc/ZoneTick
+	src.verbs += /client/proc/TestZASRebuild
 	//src.verbs += /client/proc/cmd_admin_rejuvenate
 
 	feedback_add_details("admin_verb","mDV") //If you are copy-pasting this, ensure the 2nd parameter is unique to the new proc!