I agree that Haken opening for DT would be great for them, they are not too established to do that, certainly not in the UK. We’ve had the likes of Porcupine Tree open for DT over here and, even back then, they were far more known than Haken are now. Would give more exposure to Haken, just as it did for Spock’s Beard, Pain Of Salvation and others. Haken are also fans of the band, they were actually stood right in front of me at Manchester Apollo on the AFTR show and were loving it, hugging each other and singing along to the SFAM stuff in particular.
All that being said, my preference would always be for the Evening With shows if the band feel that it is not a problem or putting them under too much strain.