So, after talking dozens of times in interviews and Q&A about inventory problems with all the new recipe materials, gear and jobs in 3.0 the solutions is...[2.0] Players can now hire up to eight retainers.
* Players are normally limited to two retainers per character. To hire additional retainers, please use the optional retainer service
You can pay more retainers.
So it's impossible to adds a few more spaces to the armoury chest or increase the retainer capacity but it seems that allowing us to basically pay twice as much per month is completely doable.