You're using your noggin on this one! Sounds like you have quite a great strategy. We mourn the loss of the plants that don't make it, but as you say they may not be meant for the climate. Long droughts a can be hard, even with thick mulch some of plants stills suffer. I've been spending my labor lately hand watering with 5 gallon bucket and while it's a lot of work, the hope is once the plants are established, they won't need watering. Time will tell.
I like your idea of different mulches, that makes a lot of sense. Ya know even without any mulch some mod the native N fixers (false wild indigo) still are doing great.
Arduous but noble.
I think it's important to be circumspect with the plants that grow in your area. If they don't make it, they weren't meant to be there, and if they're going to take a lot of labour to nurture, maybe they aren't meant to be there either. I've learnt to be a little more ruthless over the years. When I moved to England years ago, I'd lived through 8 years of proper drought with major water restrictions - Jamie couldn't believe how thrilled I was when it rained - the drops of water seemed miracles and I just hadn't seen rain for a really long time. We're not officially in drought now, but that time sticks in the conciousness of those who lived through it, and I really hope we don't suffer another one. Rain is so precious.