Sure, it obviously "can" be mixed together, but similar to how I haven't once seen the Bomb/Balm mechanic actually trigger since mixing expansions, I'm not sure it 'should' be mixed.
For now we're content to play with just the new stuff, and just absorb as much of the new content straight to our brain, but I'm trying to see if I should keep it stand alone, or alternatively, start creating 2-3 subdecks of WDPTAL games for the purpose of:
1. Excluding writing mechanic legacies cards from random environment play where its 'too much' for new groups with no social overlap. 2. ensuring cards that work directly with one another are in a small enough density that its notably more likely that someone might actually have card referenced by another card.
Either way, seeing it at my FLAGS was 100% insta-buy. Too bad I missed the kickstarter, seemed like quite the 5 day ride.