The recipe looks OK for a Pale Ale. Mosaic is a daughter of Simcoe, which is why usually they pair well together. Mosaic can bring blueberry, pine, citrus, generic tropical, with Simcoe bringing in pine and resin notes, earthy and sweet citrus. So the combo will definitely be good.
1 lb Crystal 20L is a lot and will add sweetness to the beer, maybe more than yoiu think, due to the amount of hops you are planning on using.
I would just get rid of the Crystal malt altogether for any pale or IPA recipe. Flaked wheat, Flaked oats, Malted oats, maybe a bit of White wheat, Rye, Spelt, 15-25% Vienna can be used as an alternative. My personal opinion and taste says that any hop forward beer, will be better, cleaner, crisper and brighter using only base malts.