On a Mac or Linux computer, even an old one, it is possible to play a 16x16 embark. I believe it should also be possible to run a 16x16 embark on Windows with the large-address-aware patch. The trouble with 16x16 embarks is they just run slowly. I did run a 16x16 embark with a river flowing through a lake and it went at about 5FPS on a laptop, back in 0.31.12 or so. I'm considering establishing a 16x16 site just for the hell of it. I believe the 17x17 sites just were not meant to be played or reclaimed, though we can clearly use embark anywhere to start on them.
Personally, I think when the new version comes out, it would be important to do some optimisations or even simplifications to the calculations so the game just runs faster. I believe this will become a requirement by the natural enlargement of the game, just as restoring sites and having worldgen stuff carry on into gameplay were forced by the new development choices. A similar thing is happening over at Kerbal Space Program (KSP), where the expansion of the game has reached a point where optimisations have to be made, else the RAM usage will become ridiculously large and cause trouble with making the new additions. One of the changes to be made to KSP is a method to offload things out of the RAM when not in use, and something like that might work for Dwarf Fortress.
This was probably brought up before, but what happens to worlds generated before this release? Will they still be functionable or are all previous worlds now only worth of archiving? (or something like being reseeded...)
What I'd like to see are tools or ways to import over old worlds from 0.31.12 or 0.31.25, which can hack in the missing material. That, and a way to hack in some new modded plants and have them show up in region tiles without regenerating the world.
Are animal populations going to regenerate properly in the new release, so we won't be running out of two-humped camels or giant kangaroos or naked mole dogs or other !!FUN!! creatures just from the environmental impact of a 400 dwarf fort?
What about cave fishing, is that going to work? Also just a little reminder dwarven milk doesn't show up because purring maggots are in cavern layer two rather than one. If a dwarf fortress or deep site extends down to cavern layer two or three does that give the dwarven civilization access to the wood and creature products from that cavern?