For small scale bag filling, you can get a commercially made piece of plastic with a cut-out made to hold the bag neck and some stands.
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Not great Pix I'm sorry but these are both commercially available but at $45-$55 respectively it wouldn't take someone very creative to come up with a home made version. Have a look at the bag holding cut-away on any milk crate if you want the sizes, looks like a hole saw and two straight cuts is all you need. That and a bit of light sanding to get rid of any sharp edges.
Someone could even get them make for resale.
Other option would be to manufacture a box with the cutaway in the top flaps, would ship flat, would take a hot fill and makes a great way to store the wort and with a bit of thought could be fermented in...
I have had to do some small bag filling ~5-10L, ended up using a very large stainless Bain Marie tray (smooth pressed stainless with no sharp edges), one of the plastic bag supports (above) and a silicone bung with a hose through it. The whole lot went on the scales and fill to weight. Remove the bung and just press on the bag until the liquid comes up to the neck of the bag to exclude any air and fit the screw cap (well mine was a push in tap but same same).
I think these are going to be an interesting and useful product, I can just remember when Coopers sold Wort in a bag and people fermented in the bag, that's early 1970's. Back in the day Mal at ESB tried doing fresh wort kits, bag in box, there were some issues with forklifts hitting them in transit but they worked well if handled carefully.
This is hardly a new idea, but I suspect the materials have improved over the years, as has the market size, probably a product whose time has come.
Mark