The Xperia Z2 Tablet isn't the most high-profile tablet around, but there are more than a few fans of Sony's unique industrial design. Combine that with the company's unlocked hardware (at least for non-carrier versions), and you've got a perfect candidate for custom ROMs. The CyanogenMod team has started publishing nightly releases for the Z2 Tablet, in both its Wi-Fi (castor) and unlocked GSM (castor_windy) flavors. The first nightly build is available for download now.
Sony's skinned version of Android runs on top of KitKat on the Z2 Tablet, but the company's software load is pretty high, jamming in all sorts of apps and features with varying utility. Loading up CyanogenMod should give owners a choice that's closer to "stock" Android (4.4.4), albeit with the ROM's bag of extended settings and options. Nightly builds are always a bit of a gamble in terms of reliability, so it might not be advisable to dive headfirst into CM without a backup. Here's the Gapps package for the Google Play Store and related services.
A note on the recent announcement of the Verizon LTE version of the Z2 Tablet: yeah, not a chance. Verizon infamously locks the bootloader on every Android device it sells, and though this will be the first Sony Android device on Verizon's network, Sony has already shown that it's more than willing to accommodate the carriers. Unless someone breaks the bootloader after the tablet is released, which is by no means a given, the Verizon version will probably have limited ROM support.