While extra challenge modes would be nice, I think the high valued targets are a nice pve addition. Both to solo and group play.
With phoenix credits not being such a baseline currency to acquire stuff ever since the reroll cost of gear moved to normal credits, I personally feel less need for additional CM;s. PC's are pretty much reduced in value. Getting up to cap/1000 can be done fairly quick for that one item that may or may nod appear on a weekly reset
If I may ask, whats your motivation to have more CM's? Additional group content?