Celestial Lions are a great choice
although I'm generally dead-set against most noblebright in the 40k universe I actually quite like their fluff. I think most of the reason I dislike noblebright is it tends to be implemented hamfistedly, whereas these guys seem pretty well done.
I would pay attention to how much of the scheme is dominated by gold (and that's coming from me who is pretty much Mr Mono-Colour). Not that it's a bad thing at all, or even something to be concerned about, but it's something to pay attention to. I've found you can actually get tons of variation in shades of metallics with very little effort (and very few paints) though
Gold with a Reikland wash. Gold with a Reikland wash and go back over with the base gold. Gold with two Reikland washes. Gold with a Reikland wash and a drybrush of a lighter gold/silver. Gold drybrushed over a black undercoat. Gold drybrushed over a brown undercoat.
All of that will come up with some really different textures of gold that you can use to break up and differentiate between different materials in a Marine's armour (like the main panels, pauldrons, trim and embellishment, flexible joints etc.), and all with maybe 5 colours. 80% of that can be done with 3 colours and a spray primer.
Oh, and I strongly encourage you to have a crack at weathering. It's something I've just discovered and it's both dead simple and would look awesome having these shining golden warriors looking battered and worn. Nothing but Rhinox Hide drybrushed upwards
can always paint back over if you don't like it