.......passable on a moderately loaded touring bike? Don't mind pushing/carrying a bit, but not into Nick Crane style ascents.
If spotted a couple already - Tizi-n-Ait-Imi (2910m) and Tizi-n-Ait-Hamed (3050m).
Since they're actually marked on the Insight Morocco map then I'm assuming they're passable.
But are there any higher than these?


That sounds like quite a promising route even though I'm not familiar with it myself. I reckon you'd be hard pushed to find higher passes that are particularly rideable. You can get a map of the Mgoun Massif which has more detail of that area than the Insight Map. It's printed by West Col Productions and I got my copy from Stanfords.
From my experience of cycling through that area, the faint lines that you are following can be hard to follow and sometimes not much better than no line on the map at all so be prepared to ask for directions and if you know a bit of French that can help. But if you get hold of the Mgoun Massif map you should be OK.
A mule can be a cheap assist up to the high passes if the going is looking impossible (either too steep or too hard to find the way). I passed over that range a bit further west (just north of Amezri on your map). The pass was 2860m but I did need a mule both to carry the bike and for the guide to show me the way, I hired him the day before in his village and it was a four hour hike up to the pass (only the bike goes on the mule!) where we parted and he went down to his valley whilst I went on to mine. The descent was just awesome.
Getting as far as Ait Bou Guemes by the major road will be no problem and even involve some tarmac. The eastern route via la Cathedrale and Zaouit Ahansal is a bit tougher but doable.
Go for it - should be a fun ride, but try to get that map!
Here's my website. Part 3 and especially 4 of the journal cover near to the area you're thinking of.
http://www.mattcarter.co.uk/Morocco/Morocco_MTB_Main.htm<BR><BR>Good luck!
Matt