[cypher]

I know a planted natural cage does sound like a lovely idea but unfortunately it doesn't work for hamsters, having compost in the cage will encourage moulds to grow & plants need water & sunlight to grow which is exactly what you don't want in your cage.
You can grow things for your ham to enjoy including wheatgrass & just leave them in the cage for a few hours or overnight if you'd like to try that have a look here.
Sprouts three ways!
Coconut fibre isn't a good substrate for hamsters, I don't know where you are but paper based substrates are about the best & in the UK most of us use Fitch.
If you're planning on getting a syrian then just a sand bath is enough, they don't need large areas of sand & the space could be used for more suitable things.