Well you can.......but
The market for that doesn't work. The PFA coaching scheme continues to languish in the doldrums.
So the freelance CRI can't charge anything but has to get himself trained and then find people who want his services. That involves advertising and marketing, more irrecoverable expense. Club pilots will continue to do their revalidations with club instructors, which leaves private owners, not the easiest people in the world to market to, and given the choice would you prefer to spend your hour with an experienced FI or a CRI?
The answer's not to fragment training more and to introduce dumbed down ratings (what next, Daily Inspection Instructor's Rating?) but do away with dogma so people who want to instruct (rather than use it as a stepping stone to something else) can recover costs without the expense of acquiring licenses and medical certificates that they neither want nor need and which confer no tangible benefit to the end customer.
Mike