You're going to a lot of expence and bother just to get an extra sat or 2, I think you would get 23.5E easily on the 1M dish with a spare lnb, (are you not going to motorize the 1M dish),
I've a motorized dish for about 20 years now and I hardly ever watch 23.5E or 16E, you won't get much there that you can't get on 19E or 13E,
the sat I would watch most is 19E, (at the minute I'm watching Sport 24 at 20W on my Freesat box),
you could temporarily set your 1M dish up with your sat box in the shed to get either 23.5E or 16E, & watch the channels for a while just to see if it's worth the bother.
In my opinion, If you can possibly do it, a seperate motorized dish just for your own use is the best option, then you can watch whatever you want on any Sat & get live sports feeds as well, with the right box.