+ 1, and make a model that works better with modern saddle rails that are less angled in back than Brooks' rails which are close to vertical. The Nitto device cants the bag down with modern saddles.
I made a much cruder -- but still very workable -- version with arms angled slightly upward and that held a bag more or less horizontal when mounted to the rails of my Flite. But since I don't braze I had to be content with bending and that meant thick aluminum sheet that wasn't as strong as one might want --- tho' I had no problems carrying 30 lb loads.
Note that Carradice carries a number of saddlebag supports, their prices are very reasonable, they answer questions quickly and cheerfully (or did up to a few years ago; have not ordered from them since ~2020), and that they ship quickly and efficiently and quite cheaply from Nelson (Lancs), England.
https://carradice.co.uk/collections/bag-supports
I've used a number of their supports and they all work well.
Take a look at their bags -- cotton, nylon, transverse, bikepacking, front, folder, panniers; some very interesting designs and all well made if not as Vuitton-like as Riv's bags.