Re: Titles of Office and Desert Units
Titles
One aspect of the provincial titles is that most gain loyalty over time if you leave them unassigned - 10 turns or so. So, if you want to give a starred province, like Normandy, to a low loyalty general it's better to hold off for a while, and see if the extra loyalty shield gets added. Patience, they say, is a virtue.
I've not noticed this with the offices of state, though.
Desert Units
On the deserts subject I'm with the auxillaries too. Bulgarian Brigands are another useful desert fighting unit, and are often offered in Inns when you're getting close. I've had a BB unit that had chased routers to the edge of the map, only to meet a reinforcing Ghulam Bodyguard unit coming in. I thought the BB's were done for, but they retreated, turned to fire, and retreated again. The Ghulams were too exhausted to catch them, and eventually, at half unit strength, they turned and fled.
I'll always consider the mercenaries for desert fighting - Saracen Infantry, Muwahids and Turcoman Foot often come up, but rarely Camels. You'll find that the Inns are almost suggesting troops for you to use, which might be helpful even if you don't hire the particular unit.
Likewise, it's handy to bribe an Islamic garrison for the purpose, if you can.