Related to this question: What would happen if you tried to start an engine with the cam gears meshed
Why don't valvetrains use an idler gear between the cam gear to keep the cam gears in sync, to simplify timing? Through this one could either have a chain running to one camshaft and a gear keeping them in time or a chain over both gears with service then simplified such that you can just time the crank to one moving part instead of two.
I can see the concerns being more moving parts and therefore more places for wear to occur, and weight/inertia.
Would this setup work? What would be the drawbacks? I have seen setups with crank chained to one gear and that gear to the other, but not with a gear intermediate.