Although it was a golden opportunity for Ashton to exact revenge on Mera. He decided it was best to take care of her for the last. Jonathan and Mera might not be on completely good terms, but as a father, he still cared for her.
It was for that very reason, he went as far as protecting her from the clutches of the Conundrum. Therefore, Ashton wasn't entirely sure how Jonathan would react to Ashton attacking her. Also, if he were to attack them, it was likely that the Morgans and Gruntas would go into hiding.
Making it a difficult and time-consuming task to look for them afterwards. That's why needed to plan every move of his before prematurely engaging in a battle. Although he did not doubt the ability of his soldiers, their numbers weren't large enough to fight all three of them simultaneously.
"For now, it is better to develop the city and establish some important connections before doing something impulsive," Ashton mumbled while laying in his bed.