The definition for Mortgage Loan Originator can be found at 12 U.S.C. 102(b)(1) but it simply says that a MLO is an individual who:
1) Takes a residential mortgage loan application; AND
2) Offers or negotiates terms of a residential mortgage loan for compensation or gain.

In your message you didn’t stipulate that your Lending Assistance only have a customer sign docs and tell about the terms on the note when it is being signed, for specific types of loans. That being said, if they do those duties on what qualifies as a residential mortgage loan (see .102(e)) then yes they would need to registered. That is as long as they get paid.

Remember that it’s a 2 prong test: they have to take applications AND offer or negotiate terms for compensation. They have customers sign docs (sounds a lot like taking an application) and they tell the customer about the terms (sounds a lot like offering terms to me). I think they fit both prongs of the test.

Good luck with getting them registered; at least you’ve got some time to get it done.