the way i see it is looks like it all would work ok but
seem to notice some of your neg switching circuits are back to front
like hand brake switch.
ie. the feed is live from the ign on sw to the bulb (live all the time) and the h/brake switch earths the bulb completeing the circuit as the switch (earth switched) will only have one wire and saves exsess wiring.
bit like a oil pressure swith say.
this is done because it makes the system fail safe as most of the wiring would be on the neg side and if the insulation was damaged it would make the it go to the warning state.
dont think you need a relay for the horn as most horns are earth switched but thats up to you just copy how the orignal car did it if your not sure
you could use double gang relays say for your headlights (one coil two switchs) and fuse the feed side of the relay
you need to protect the battery side of battery by moving your fuses or by fitting a master fuse i have seen a few cars catch fire! buy poor wiring protection the closer to the battery is always better would be a shame to put all the time and money into your roadster . could even burn the garage/house down
the diode for the charge lamp is this not coverd buy the one in already in the alternator? i would need to check whats fitted
thats my take on it any way