Improved User Interface (UI).
There's already an active worker proposal for UI development.
Mobile App on Android and iOS.
There are several Android & iOS BTS wallets already.
Merchant Payment Tool.
Palmpay covers this, unless you mean getting supported by coinpayments or similar tools?
Listing on top tier exchange with a defined volume.
Is this not already covered by 2 worker proposals - the chinese community representative & the bitshares foundation led community representative (for EMEA).
I guess if this was to provide rewards to those who develop tools for BTS without having done a worker proposal themselves that'd be pretty neat. It could be useful for there to be an innovation worker though it's a bit unclear.
RE: Bitshares X: Moonshot Reward Fund