Full text index for a column that stores json which contains guid - Is this a good idea, space-wise?
... a full text index for a column whose values are json ... usually contain Guid (or UUID) values.
Is it a good idea to build a full text index for this column?

I would say &quot;No&quot;.
A full text index makes all of the words in the field available for searching.  I don't think that's what you want.  You want to be able to search for those Guid/Uuid values and, possibly, specific Request Types.
My preference would be to pull these values out into separate fields in their own right and index them.
Failing that, use a JSON-aware index type, which will be better, but still slower than the separate fields.