Sounds like you have plenty enough for a respectable garden, but you might want to add some Dudleya, which you can get at places like Home Depot and Target. In fact, there are some Dudleya native to the California coastal regions. Echeveria also do well, particularly the kind called "Topsy-turvy." Sempervivum would probably work.

Currently I'm growing a wide range of succulents here in Dana Point. One thing I have that's not on your list is mimickry plants from South Africa: lithops, P. nelii and another species I can never recall the name of.

Statice and Pride of Madeira are also popular here.

Here's a few that comes to mind
Aloe dictotoma
Aloe plicatilis
Aloe polyphylla
Coreopsis gigantea
Cyphostemma juttae
Fockea edulis
Pachycormis discolor
Pachypodium succulentum
Pachypodium bispinosum
Tylecodon paniculata

More Crassula. That Pony Tail Palm will take up the whole space. I love Dudley, but they don't like inland areas, the are a Calif. Coast Plant. and they must have a Northern exposures. Fockea edulis is a good suggestion, they like to climb, and will develope a great caudex if grown in the ground, I love
Aloe dictotoma I think it grows like a small tree and Aloe plicatilis. You have great suggestions above my post go for them. Norma

I'm hardly an expert on this--I haven't grown these in the ground personally. However, I used to live down the street from the Huntington, so I've seen a nice collection of plants at multiple times of the year.

I agree strongly on Aloe plicatilis as a must have--especially with all the other Aloes. I've noticed them in the nurseries a lot lately (9b, Sunset 15). This actually surprised me, as I thought they were supposed to be borderline for our climate. I gave my potted one from Pasadena (10a, Sunset 21) to my mom (zone 9b) to put in the ground after it got too big. It died within a year or two (cold, poor drainage?) You might make sure they are suited to your climate even if the nuseries are selling them.

Full grown Beaucarneas are incredibly striking in my opinion. If you like them a lot and you have the room, you should go for it. You might be trading drama for diversity, though.

Have you thought of one of the Puyas with the metallic flowers in colors that appear to be "not found in nature"? They're spiny and some are quite large. Some pictures from the web (Puya berteroniana and Puya venusta).

http://static.flickr.com/38/111805365_a006dacf2d_o.jpg
http://www.anniesannuals.com/special_pgs/pom/0612/images/puya_venusta.jpg

Others may know whether this is appropriate: Alluaudia procera. It should take up more vertical than horizontal room. I think it might depend whether you are 9a or 9b (if even those are OK)

Is Encephalartos horridus considered a succulent? I know the trunks of some cycads like this are called caudexes. Although a cycad I think it would fit in to a succulent planting. Would other cycads work?

And finally, definitely a non-succulent, but what appears to be a familiar plant adapted to a dryer environment--maybe it would fit in. Strelitzia juncea: it's very similar to Strelitzea regina, the regular bird of paradise, except that the leaves are generally lost in the adult, leaving only a reed like plant with just petioles. One of my favorites--if you're close to the Bay Area I got one at the Dry Garden in Berkeley. I see you aleady have a Strelitzea though...

Here's a beautiful photo of a plant I assume is mislabeled:

http://www.treknature.com/gallery/Africa/South_Africa/photo77511.htm

Nothing really "must have". I think living in California where we can grow so much, there's no reason not to branch out and plant the unusual things that others won't normally see. None of the above are that unusual, though.

If you have a ton of room and are very close to being zone 10, Chorisias are amazing trees.