First i'd like to say the cabin really did help a lot with build times while going through classical age. However, i feel that it gets locked way too early in medieval age. I would like the devs to consider locking it with the "Education" research, when huts are locked.
My reasoning for this is as follows. As a despot player, i have chosen over the last several alphas not to build classical siege buildings/ units. The primary reason why is because building siege in classical makes your build times skyrocket out of control and it was very difficult to get the times back down again. Well, with the cabin, i decided to see how much this building would help, so i built it to level 9 in all towns. I also built siege workshop to lvl 18, and had minimal other military buildings, as much as what is needed to build a sage tower (so, 1 lvl 5 archer tower, i enchanted tower, lvl 8 garrison - no stone age military). So even with 20 maxed houses, lvl 9 cabin, my build times were well over 100%. (Can't remember the exact numbers now, as i didn't write them down). My dwelling had a few stone age military buildings, stables, and a few more towers thanks to bulat, and the build time there was approx. 170%.
So, my first research into Medieval age was monotheism, chosen because it is still significantly cheaper compared to Education, and gives the opportunity to build up the town hall and add more huts/houses, to try and get build times down again. However, you are now hit with this research with losing the cabins, so before you can even get to building more huts/houses, you're hit with a 54% (or 60% if you used a blueprint) increase in build times. So my dwelling went to well over 220% build, other towns about 170%. I built town hall to lvl 8 in all towns and added huts but i'm still not yet to 50%.
Locking the cabin in Education as opposed to Monotheism would allow a despot player to build up the town hall and try and get a handle on the already high build times before it gets increased again when cabins are lost.