While it's true smartphone hardware become more powerful, it's not the only limitation. Theoretically, Wasabi Wallet need to run in background while connected to the CoinJoin coordinator and doing some stuff (choose input, sign transaction, etc.). And since Wasabi Wallet use Tor by default, Tor also need to run in background. I expect it could drain battery quickly and the OS show warning about it. CMIIW.
What if, when you first launch the application, you can prompt the user to select by default what type of connection will be used to connect (for example, only Wifi). I know that this can be done in the phone settings, but few people worry about it.
And the mobile Internet will be used “only when using the application.” My point is that if the mobile Internet is not used to work in the background, then this will not affect the battery drain in any way.
Although, to be honest, I'm not sure how to implement this.