Ah....yes, hadn't thought of voice assistants. I don't use them much.
The issue with setting a default level and color temp via an app is that if you turn the light on by setting it to another color temp/level, what you just commanded would be overridden by the app sensing that the light was turned on.
What you really would have to do is to use a virtual device with a custom driver. When that device received the on command, it wouldn't issue that command, it would setColorTemp and setLevel to what you told it to. You could then mirror that virtual device to your real device. Then, if you turn the virtual device on by setting level, it would set it to the level you chose in the command, not the default.
That's the problem with trying to solve a device issue at the app level. The solution isn't going to be 100% applicable but it will be 100% executed.