1E and 1F were actually originally intended to be used as record and unit separators, respectively, so that’s actually not a bad idea. The description for those fields in the article you linked even mentions that they’re suited for use as field delimiters.

Generally a bad idea to use in-band signalling like that. They won’t do anything weird but consider what happens if the actual data contains them.

Depends on if you want your data format to be strict ascii. If you don’t care, then sure, why not?