Couldn't you take a liquid yeast pack, make a starter, and then split this into vials that can be scaled up via future starters instead of harvesting yeast post batch fermentation? I was looking into yeast harvesting to save some money and it seems like the same concept without having to worry about doing it all after batch fermentation.
Sure, you can do that. Keep in mind that storing, culturing and pitching healthy yeast from your personal laboratory is not as simple as it seems. If you want long term stability you need to have a robust protocol in place, along with the ability to maintain a sterile environment. But it is not something beyond the scope of a homebrewer. Way back when, in the Papazian days, we didn't have the luxury of having Fedex delivering any imaginable liquid strain. We used a yeast slant (and we were happy damn it). If you have the time and desire you can start a yeast library. But the time and effort is greater than the cost savings for most homebrewers. If you can get 2 or 3 brews from one yeast purchase that is usually enough, in my opinion. Cheers.
