I prefer simplicity myself, the less there is, the less there is to go wrong. i also like the idea of splitting the lights, one AC, one DC for the fact that you are drawing on two different sources available without overloading either. The DC side is relatively unused except for signals, brake and tail and instrument lights.
I would leave one headlight as stock, through the switch and wiring you already have, the AC light would function as normal. The DC light I would run through a relay from the fused and switched battery source available. I would use a 5 prong relay with the 87a and 87 connectors on them. The relay connects 87a while at rest and 87 when activated. Connect the low beam to the 87 and when you turn on the key low beam will come on automatically if you have it wired from 30 to 87a. (alternately you could mount a separate switch to be able to turn off that light independently)
For high beam I would trigger the relay from the existing high beam switch wire through terminals 86 and 85. Both lights will come on automatically, though the AC light will have to wait for the engine, and switch to high beam with the one stock switch.
If you were to change your signals and tail and instrument lights to LED as I have it would also free up more amperage for other options, such as heated grips, while not overloading anything.
Sounds good in theory in my muddled brain, the only grey area I can think of is whether the relay will trip on an AC source, haven't experimented with that yet. I suppose you could add a diode in the switching circuit to straighten out the waveform if needed.
Just my $.02