Quick question: What version of TESB is Masterwork 1.09 using? Curious as to whether it's safe to upgrade an existing savegame to 2.11.
I honestly dont know. I'll update to its newest state for the next release, 1.11. Dirst is super helpful and I feel bad for not doing this already, but I usually work on a single topic at a time. If I update TESB I'll update all the other third-party mods too.
Masterwork 1.10 is running v2.08 of The Earth Strikes Back!, but has the readme file for v2.03.
The short answer is that it's not safe to update a v2.08 save with v2.11.
With a little work, you can drop v2.11 on top of a copy of your Masterwork install. Just make sure you do it to a copy with all the settings you want (with TEB enabled), don't overwrite
anything vanilla while unzipping, and follow the instructions for the
.insert files tucked in the zipfile. The onLoad.init won't update, but fortunately that stuff hasn't changed since v2.08.
Meph's GUI ought to be able to work again after all of that (with the same bug that the Pet Rocks choice doesn't do anything), but you can't be too careful making backups before changes.
Edit: Re-read the question, Masterwork 1.09 is also using TESB v2.08. Answer is the same... Cannot update an existing save but could prepare for a new worldgen.