Currently reading Very Special Ships: Abdiel Class Fast Minelayers of World War Two by Arthur Nicholson and while I had some knowledge of the type and its flexibility I never realised just how useful they were. I had been aware they had been used as fast transports for troops and material as well as, blockade runners but I was surprised they were also used as assault transport (sometimes against orders) and could have made very interesting fast APDs. Things that could have been better was their range, which would have required a larger hull and more powerful machinery, another was their AA capability, which extra length would have made easy to improve.
What I am thinking is the RN developed a larger fast minelayer intended for operations in South East Asia where range and improved AA would be very useful and then evolved the design further once it was realised how flexible the Abdiels were. They could be based on an Arethusa/Dido Class cruiser hull (thankyou Flyhawk for their new 1/700 HMS Aurora and Naiad), with no, or reduced armoured belt and if possible double the Abdiel's machinery with three funnels and four shafts. A flush deck covering the mining deck, provision to carry LCVPs and improved facilities to accommodate troops, in particular Commandos. It would also have either three or four improved DP guns 4.5" QF Mk IV in BD Mk IV mounts, two Quad 2pdr Pom Pom or multiple 40mm Hazemeyer twins.
The idea would be that they would have been ordered at the outbreak of war for the RN and RAN to serve in SEA and based on experience with the Abdiels, destroyers converted to fast transports and APDs, they were modified to fill the Assault transport role once the Japanese fleet had been successfully interdicted in the theatre. Post war they continued in a variety of roles including mine warfare training and tactics development, assault transports, as well as developing small unit amphibious tactics.