I agree. LVMs and encryption are now deal breakers for me when it comes to choosing a distro, which is one of the reasons I recommend OpenSUSE, Debian, and even Kubuntu over many other distros (the other being good support for KDE). I was looking into installing Mint but was a little bit dismayed that its installer will not work because it can't pick up my encrypted LVM.
I think a great way of handling this would be to allow installation via the Debian installation framework (either the text or graphical tool, but prefebly both) AND using the live installer. I actually would prefer a non-live install disc, but I guess I'm just old school boring like that. It could be added as an option at the boot screen and would essentially provide instant support for LVMs, encryption, etc. And since most of the work is already done, only a few simple adjustments would really be necessary such as creating proper branding on the GUI version and ensuring the proper programs are selected by default.
Really, Mint seems to be the "perfect" distro right now, and I love that it has a development team that listens to its users, implements the best solutions based on its users commentary, and actually does a lot of development work. Cinnamon, MATE, and the Debian Edition as great examples of where the Mint team has went above and beyond to show that they are serious about making things work and innovating beyond the base. After seeing them in a working state, I think asking for good LVM and encryption support should be a snap to implement.
This is one of the few distros around that do any real innovation on a major front and really it is just a community supported project. I do think that Mint should take a next step to supporting LVMs and encryption simply to cross that bridge into enterprise territory. If businesses are to take Mint seriously it needs to provide the same full features as Debian, Ubuntu, Fedora, and SUSE. And really, being based off of Debian / Ubuntu really gives the project a major head start.