Better or not, the M2000 can do things Mk1A cannot, like penetration missions. With 12 jets, and M2000 only expected to retire by 2045, yeah, it makes sense. We have 50 jets in 3 squadrons. So we can either add these 12 jets to existing squadrons or create a new half squadron, I guess it depends on whether we want to upgrade the jets to the current standards.
These jets add value even if Mk2 comes in.