TL;DR
Barreling recipes should be unlocked when both the technology and fluid are unlocked.What?
Currently, barreling and unbarreling recipes unlock all at once. This can be overwhelming for new players, while also being misleading as most of said recipes are not unlocked until a later time. I believe that the barreling recipes should be unlocked dynamically, allowing for the recipes to only show up when barreling has been researched and that fluid has been unlocked. This can currently be accomplished with a mod script, but i wouldn't mind seeing this in the base game. For when a fluid is unlocked multiple times (i.e. petroleum gas from basic oil processing, advanced oil processing, and coal liquefaction) the barreling recipe would be unlocked on any of those technologies being researched (but since basic oil processing is a prerequisite for both, in this case it would unlock on basic).Additionally
TL;DR special sub-prototype of items.It would be nice to have a prototype that you can call "compressed" or "boxed" items. In the base game, this would just include barrels of fluids. But for mods, this would be stuff like stacked items from Deadlock's Stacking, the crate system found in Exotic Industries, or the various forms of fluid canisters found in Pyanodon's. This item prototype would have a base item (barrels for vanilla, but could be nothing), specific entity requirements for compressing/uncompressing recipes (Assembling machine 2 and 3 for barrels), and compression amount (for barrels, 100 units per barrel. Could be a per item basis, or static). You could add items/fluids to this group on initialization of the group or when creating the items/fluids. If the compression amount was per-item, then that is when you would set that amount. Recipes for barreling and unbarreling would propagate based on this data. This isn't a necessary feature, but I do think it would complement the changes do the barreling unlock.