I would go with at least 50% Rice syrup, and the rest date syrup and maybe another sugar. Consider Belgian Candi Syrup (Home brew shops should have it). I've used that in the few brews I've made. Add some maltodextrine if you can find it. I think it will turn out just fine.
Just do a small batch and see how it turns out, then adjust your quantities from there.
Just to start simple, I'd try something like this:
6 gallon batch.
3 lbs Rice Syrup(prior to boil)
2 lbs Date Syrup
1 lb Belgian Candi Syrup (D45) OR 1 lb of a different sugar..
0.5 oz Magnum Hops (60 Min)
0.25 oz Saaz (15 Min)
1 Whirlflock Tablet (5 min)
0.25 oz Saaz (flameout)
1 pkg Safale US05 Yeast
I adapted this from a random recipe I found, so I don't know anything about the hops. Maybe someone else has a better hop suggestion. But this should be a good starting point.