procedure RegisterProc(const Page: string;  ComponentClasses: array of TComponentClass);
begin
  if not Assigned(RegisterComponentsProc) then
     CreateRegisterComponentsProc;
  RegisterComponentsProc(Page, ComponentClasses);
end;

procedure RegisterProc(const Page: string;  ComponentClasses: array of TComponentClass);
begin
  if Assigned(RegisterComponentsProc) then
    RegisterComponentsProc(Page, ComponentClasses)
  else
    LogPrematureRegistrations( Page, ComponentClasses );
end;

var RegsLog: TList<TPair<string, TArray<TComponentClass> > >;

procedure LogPrematureRegistrations(const Page: string;  ComponentClasses: array of TComponentClass);
var L: TPair<string, TArray<TComponentClass> >; i: integer;
begin
   if nil = RegsLog then
      RegsLog := TList<TPair<string, TArray<TComponentClass> > >.Create;

   L.Key := Page; 
   SetLength(L.Value, Length(ComponentClasses));
   for i := 0 to Prior(Length(ComponentClasses)) do
       L.Value[i] := ComponentClasses[i];
   
   RegsLog.Add(L);
end;

procedure RegisterRegisterComponentsProc( const handler: ...);
var L: TPair<string, TArray<TComponentClass> >;
begin
   if not Assigned(handler) then raise ....;
   if Assigned ( RegisterComponentsProc ) then raise ...; // запрещаем подмену обработчика другим, если надо

   RegisterComponentsProc := handler;

   if nil <> RegsLog then begin
      for L in RegsLog do
         handler(L.Key, L.Value);
      FreeAndNil( RegsLog );
   end;
end;