Coinomi can support POS coins but it cannot stake. The reason is that to verify that a block signer can actually sign the block it needs the full UTXO set that can be several MB in size. One solution is for the POS coins to create delegate keys for the actual staking (but not spending) and leave the master keys in the lightweight wallet.

The trusted servers are plain electrum servers in some cases modified a bit to support each coin.

For the payed integration you can send us to support at coinomi.com.

The hardforks are tricky business because we need to manually update the underlying peer-to-peer node. Fortunately the forks are rare (except in Dash) and the developers usually inform us about it.

Android: It is possible to centralize the blockchain (like MultiBit and Electrum for Bitcoin) whereby the client connects to
remote nodes and reads the chain directly from there, without downloading it?