A bit of information on the German guilds (I think this was more or less the same in whole medieval Europe, but not as extreme):
The guilds were very selective and it was very difficult to join a guild, because the members didn't wanted to get competition. This means, that especially craftsmen with good and innovative ideas were not allowed to join a guild (side note: the difficulties of becoming a member of a guild was the reason why widows of master craftsmen were very attractive for younger men, because marrying one means that you could become a guild member almost instantly). This restrictive policy resulted in a major lack of innovations in almost all trades. There was defacto no competition at all and no need for developing new ideas, techniques etc.
Regarding your idea of a shoemaker making pouches or something other out of his scraps would not have worked in the later medieval gild system, because a shoemaker who sold a pouch, a belt or something else committed a crime and had to face very high fees. This is why there was an own guild for all the different parts of what we call leather working in general I.e. shoemakers, saddle makers, belt and strip makers, harness makers, glove makers and so on and so on.There were different guilds for different kind of tanning hides too.
The shoemakers even put it one step further in Germany. There were shoemakers (schuhmacher) who actually build new shoes and other craftsmen who repaired old shoe (called flickschuster or schuster, maybe the difference in the English words shoemaker and cobbler expresses the same).
Maybe that helps you. Would like to now more about your presentation and how it turns out.
Greetings
Jonathan