@GunsAreFun Yeah, I do use a bladder. There isn't a standalone sleeve for the bladder - although there is a specific opening for the tubing. I use a 2L bladder and initially I just used some paracord to hang it from loops inside the pack. I would often use other internal straps to keep it from moving around. Eventually I bought their Stalker 500 when they had a sale going. It can hang in the 5500 LT and serves as a bladder sleeve and I use it to organize a few other things. You could take it out and use it as a small day pack but I rarely do this. Sometimes I will use it when I'm scouting or fishing and just want a small pack to carry a bladder and some snacks. Not having a dedicated space for the bladder on the 5500 seems an odd design choice but wasn't a deal breaker.
As others have suggested, if you do go Kuiu and can wait a while they do have pretty good pack sales at various points throughout the year.