Re: chaser's packages

Yes, you're really dealing with apples and oranges.
A "chaser's pass" for a mainline excursion has some merit - there are those (like me) who don't consider riding a train fun, and would rather be trackside. If there were a mechanism to support that mainline excursion as a chaser (other than buying a ticket and leaving a seat empty on the train), I'd gladly pay it.
For photographer's specials, there is actually an argument to be made in the other direction - that offering a less expensive option cannibalizes your revenues, and may lead to cancelling the trip.
To garner the support of a chaser for a tourist railway, many British preserved railways have a special class of membership that allows lineside access under certain conditions (hi-vis vest, take a safety briefing, etc.). One could adapt such a program, but the question then becomes one of the administrative overhead vs. the revenue. If the program brought $1,000 to the C&TS in a year, would it be worth the effort?
We haven't discussed whether doing so puts you at risk of liability if your chasing customer wrecks and sues you . . .
All in all, the reward is low and the overhead and risks hard to quantify - which is probably why no one does it here.
JAC