I've been getting into the Doff missions a whole lot on my main lately and have been steadily increasing the amount of Doffs I have at my command.
I'm currently sitting on 151 blue and purple Doffs and find it incredibly easy to reach the 20 mission limit. As it stands I have no need to purchase the next two 100 Doff roster slots since there's really nothing I'll be able to actually do with these Doffs.
With that in mind I'd love to see the addition of Doff assignment slots in the store. They could be sold in sets of 5 or 10, up to a max of anywhere between 40 to 60 or so. I wouldn't blink at something around $10 to $20 for those.
It would not only be something I'd be willing to purchase, but it would also entice me to purchase the rest of the Doff roster slots.