Actually they served with the CMF (reserves) until about 1955, alongside the M3 Grants. If you game Balikpapan, you can include a Grant dozer and a Covenanter bridgelayer in your box of toys.
For ‘what ifs’ there’s always the Matilda Hedgehog, the same Hedgehog spigot mortar set up used to sink U-boats but bolted on a frame to the rear of a Matilda For post war colour, the ‘not quite a Sexton’ Grant hulled Yeramba SPG is a fun beast. Still not tired of Australian silliness? Eureka and Company B produce the AC1 Sentinel for those wanting something for home defence.