Let’s say for one week, they decided to make invasions be affected by the infamous boss known as Zuul’goth. That would mean, at the start, you are dealing with a bunch of grunts up until level 10 which is where a tower will appear along with the mini-boss from Raid. This tower will then reappear on the second mini-boss and then permanently part of the team with Zuul’goth.
This goes up to level 40 where another one of the 2 grunts gets replaced with another tower.
At level 60, the final grunt is gone and replaced with a 3rd tower making it 3 towers and 1 Zuul’goth.
Now, at level 80, maybe Zuul’goth can start suffering from it’s other variants and changes into one of those other forms like Dark Zuul’goth or stuff like that.
As for rewards, due to the difficulty, I would imagine a lot better rewards, than what we currently get or hell, even doubling the rewards due to the fact it is two for one and how it is scored will be based on total damage to both Zuul and towers (Scores adjusted accordingly).
In fact, it would not only be a good time to bring in the towers as craftable soulforge exclusive troops (Just make them 4K of the colored shards) but should also bring in a new boss troop able to destroy both towers and Zuul with ease.
Either way, just my thoughts on a matter that I wondered how well or messy it would go.