https://www.aerotime.aero/rytis.bere...e-unions?v=amp
The quotes in this article take care of the scenario where unions start pushing their way in a given base. The base will simply be shut, likely resulting in job losses, and capacity will be moved elsewhere. Which may still allow for most routes apart from the domestic ones to be preserved.
Forget about making a LCC comply with unions, especially in today's climate. They all have far too great resources to get caught and killed by any union. While many give RYR as an example of the opposite, they often forget the unpalatable bit of the story - which is that they have got Buzz, Malta Air and Lauda Europe which were set up in a way making them immune to the union recognition arrangements in place with RYR. And a large part of all employees of the RYR group work for these companies, where they aren't any more protected than they would have been with WZZ.