the wiring was designed to meet the regulation of the day in the UK. so the park light was a circuit on its own, you could pull the key and leave the bike with the park light while in the bar for a beer or two or more, and the silly little blue capacitor would still hold the juice to get it started on points.
the biggest battery drain is the tail light on all the time and the need for a front light (as of 1974) which pushed the alternator to its limit at lower rpm.
I have planned a second wiring harness from scratch. the first turned out OK, it was based on using the original ignition switch but i added a 4 fuse panel . if you go to a simply of/on ignition switch you may want to think about a fuse panel with dedicated circuits for lights, signal lights, brakes lights, ignition etc and a few relays too. at which point i'd want about eight fuse slots
also i tried to eliminate all the electrical joints possible, and ran from point to point . I used TXL wire which is very common now in american auto under the hood wiring,
contemplate LED's for tail light and every other light which is on steady.