I don't know anything about the Nova gene, but the pastel gene in it is definitely browning already. I would say maybe try and pick up the best looking Nova you could find and breed it to a pastel enchi to start... That way you can find a very clean pastel enchi. I really don't know to many people even working iwth the Nova, but I would personally pass on this one. The pastel just doesn't seem of the greatest quality. Just my opinion.
Nova makes pastels dark you won't find a clean pastel nova like you describe. As far as pastel enchi I'm putting my enchi to my pastel both are high quality so I expect the hatchlings should be as well
1.0 Pastave YellowBelly
1.0 Pastel
1.0 Enchi
0.1 Pied
0.1 Pinstripe possible dh albino og
0.1 Specter
0.1 Butter
0.1 Chocolate
0.1 Black Pastel Het Orange Ghost
0.1 YellowBelly Sub Saharan Giant
0.1 Mojave
0.1 Pastel ph Caramel Albino
Cool, I was going to suggest getting with Dan. It does look a bit dark to me as well but if you like it and works well into your future plans then go for it.