Default Rooting stock, nandroid, unlock, restore? Will it work?

Finally I'm (again) rooted on stock, but that GPE rom becomes more and more attractive every single day...
My questions are:
I still have my TA Backup from the VRoot days (more or less day 1), is it still actual or do I have to redo a more recent backup? The TA partition changes with firmware updates?
And then, I'm unlocking, therefore deleting any user data on my internal memory, and subsequently I'm installing the GPE rom from scratch.
Let's say I'll stay like that for a week and then I'll miss the Sony rom, can I simply restore my previous (locked) nandroid backup? Would I get any troubles from that?

Thanks for the help in advance!

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