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.