If I was an airline looking to recruit First Officers, I would stipulate an ATPL as an entry requirement. The reason for this is that you are seen as an investment to them, they are going to spend a lot of money on you, and want to get the best return on their investment.
This, in my experience is the norm in the real world. Years ago when you HAD to do the CPL first the situation was different.
So, if you want to fly for an Airline at any point, do the ATPL, it's not much of a step from the CPL.