Emergency cleansing is an issue. Girls undergoing grief spirals or dealing with severe emotional issues like Oriko went through can't be away from their Clear Seeds while that's happening. A central distribution system means they have to have their emotional breakdowns and process difficult emotions in a single centralized place instead of being able to do so where they're comfortable and where their non-meguca support network is. One of the things we've seen is that due to the way grief spirals work, girls like Mami and Kyoko survive by repressing their issues rather than dealing with them because actually processing those difficult emotions is expensive in terms of cleansing. That lets them survive in the short term, but leaves them brittle and easily pushed over the edge by Kyubey. Giving girls access to Clear Seeds means they can start actually processing those emotions in a healthy way.
There's also the issue that limiting our cleansing services to something that firmly locked down and under our control, we're making them more reliant on us. Girls get used to having free cleansing on tap, get used to that security and maybe a little rusty at witch hunting, then suddenly Sabrina starts charging... Sure, Sabrina would be disgusted even considering that, but the girls we're helping don't know that. Plus, as our organization expands, new management might get involved. Maybe Yuki starts playing hard ball. Again, Sabrina will come down like a ton of bricks on anyone who tried to pull that, but look at it from the prospective of people who don't know just how dedicated Sabrina is to her humanitarian mission, and what they do know about how other Grief Controlers have historically behaved. By making the offer to put the resources under the individual girl's control, it makes the "no strings attached" part more obvious and sincere. It makes girls more likely to accept our help.
And, of course, once there are enough Clear Seeds out there, the risk of theft goes down immensely because no one has any reason to steal if they're already living in a post-scarcity situation.
That said, I do think we should absolutely bring up this as a new option on our menu when we make our cleansing trips to groups that haven't accepted Clear Seeds already.
As for collecting Clear Seeds after we crack de-witching, I don't think we can justify collecting them at all until we have a substitute anyway. Otherwise, we'll be dewitching one girl only to have a half dozen other girls witch out because of it. And once we get something like Grief Cubes in a state to be mass produced, the value of Clear Seeds will plummet to the point we'll have a much easier time simply buying them back from girls who are no longer reliant on them.