My regs include 3 DAAM, 1 RAM (heavy yoke) and 1 Phoenix/DA. I have picked up 2 Conshelf 21S in order to dive with a newer crowd who won't let me play unless I have an oct/BCD and the rest of the PoliticallyCorrect, PADI approved gear. I figured it wasn't worth fighting if I was going on an organised trip. Who wants to be left on the dock because the Boat operator/DM is ignorant of all of the ways to skin a cat?
If I was to rephrase the question, I would like to get 2 tanks the same that will allow me to play with the modern crowd who are using high capacity tanks to get the last minute of bottom time but also be able to dive in a minimalist fashion with my older favourite gear without having weight/buoyancy issues. For example, I wouldn't want to be trying to use a HP 130 diving without a BC in a 3mm wetsuit.
Getting fills at some of the LDS can be tricky as some have it in for any old tank including 72's and none of them are open to negotiation while standing at the fill station. Buying a new tank was one option that was offered me in order to get air. Fortunately, the AL80 was very easy to sell after that weekend. (I have an older style plastic back pack that easily adjusts between a 6.9 and up to an 8 inch tank).
the LP95's look like a possible choice.