Personally, I love Brett and hops combined. I generally pair a pale belgian-inspired beer with Brett. Brux and citrus type hops (Citra, Amarillo, Centennial, etc.) to complement the fruity Brett. characteristics. Can't say I haven't ever thought about doing a dark Belgian and dank hops together before. Could be interesting? Could be a train wreck? It's homebrewing, I say go for it and let us know how it turns out.
Not sure I would add the lacose. Did you mean maltose? I would lean towards adding malto dextrin. You could also add some oats, wheat, spelt, in addition to your rye in your partial mash if you are looking for some dextrins and food for the Brett. Some of the tannins from your hops will also help boost up your body from the 3711 and Brett taking the gravity way down.
Are you using chocolate malt or chocolate? If you are using the malt, I would think carafa would be a better choice, IMHO.
I have used choc/black malt to color a Flanders, and I'm surprised at how so little roasted malt can still give off astringency in the finished product. When you get THAT dry, the astringency lingers longer than the prickliness of the acid.
I'd go with a debittered black if you're just looking for color.