Cohorts are bad crafters. When you are 9th, your cohort is 7th, and can't craft rods yet. It's a cheap way to cheat a few extra feats, but it is not free.As to crafting, I will have a cohort (at 7th) that does the crafting.
Sure, the guide assumes you are playing in a regular game, under Pathfinder rules. If your DM does not allow crafting, you won't craft. On the other hand, if your DM does not allow magic-users, you won't be a sorcerer at all.However, I'm still leery about the concept of relying on magic items for the core strategy of the character. Cash, downtime and magic item availability are all matter of DM fiat and this particular DM prefers a more gritty game and less of the core Pathfinder assumption of the "Magic Christmas tree" effect. While I fully understand that purely by RAW I "could" be using empower/maximize by 9th level, there is just no way I can be comfortable making a character that needs to rely on that build structure to be functional, walking into a game where I can't be certain those options will be freely available. Does that make sense?
In any case, in this AP, you have plenty of time to craft.