Hi. I do some part time work that requires me to take a day bag. I prefer not to wear a back pack. and as you say, it is then used to lock the helmet, gloves etc. This is the option I prefer and works best for me.
I made the rack myself, and have a lot of experience making ' 1 off ' racks and motorbike and car trailers. It was not particularly easy as the mounting points are very limited. The rack obscures the stock tail light, which remains functional, but hence the extra light. The rack is mild steel and powdercoated. Its easily removed, and simply unplugs from a connector fitted to the wiring loom under the seat. As its all LED, there was no problem with the system throwing a fault code. There are no regulations I am aware of in NZ related to bike racks but i'd put money on it mine is better and stronger than pretty much any other you'd find.
I guess the 701 is not really considered a touring bike so there are not many luggage options offered for them, and usually just for the left side. For me, it's just a fun bike while I wait for my new T7 to arrive in the country so, it is for sale, although not advertised anywhere yet. It's now done 1400k's only, had its first service, and is arguably better than new.
I've had the front wheel waving a few times, but it's not my riding style. Best regards. Geoff.