Hey Kimo,
I was afraid of that answer Filed an issue for this as well: https://github.com/SAP/openui5/issues/193
Option 1 is what I actually already did. I use a validator function on liveChange to set the value state of a control. I have the same constraints on various fields and therefore want to apply a static function. It does not feel right to extend TextField just for that purpose :/
I am a big fan of separation of concerns and therefore keeping VCs from outer dependencies as much as possible. But I am also a fan of having the freedom to do what I as a developer think is right And in this case DRY imho clearly overrules VC-separation.
Thanks for your answer anyways.
BR
Chris