second version:

- always add removed Classes to Undeclared. This might lead to unused entries, but that can happen even without the check

src/GeneralRules/ReGlobalVariablesUsageRule.class.st

@@ -21,8 +21,7 @@ ReGlobalVariablesUsageRule >> check: aMethod forCritiquesDo: aCriticBlock [
 			node isVariable and: [ 
 				node variable isGlobalVariable and: [
 					(self isKnownGlobal: node name) not and: [
-						node variable isGlobalClassNameBinding not 
-							and: node variable value isObsolete not ] ] ] ]
+						node variable isGlobalClassNameBinding not ] ] ] ]
 		thenDo: [ :node |
 			aCriticBlock cull: (self
 				createTrivialCritiqueOn: aMethod

src/Kernel/Class.class.st

@@ -883,7 +883,10 @@ Class >> removeFromSystem: logged [
 	self superclass ifNotNil:
 		["If we have no superclass there's nothing to be remembered"
 		self superclass addObsoleteSubclass: self].
-
+
+	"we add the class to Undeclared so that if references still exist, they will  be automatically fixed 
+	if this class is loaded again. We do not check if references exist as it is too slow"
+	Undeclared declare: self name asSymbol from: Smalltalk globals.
 	myCategory := self category.
 	self environment forgetClass: self logged: logged.
 	self obsolete.