What do you guys think about the GCPD blimps having batsignal projectors on them?

That way they can be focused on certain areas to show where something is happening or be used to other effect.

When it started it was more a secret and to intimidate...but with (pre52) Batman being in the JL and working with the police often maybe it would make sense?

It wouldn't really work out, even pre-52. The Bat-Signal was on occasion described as an embarrassing crutch for the GCPD. Gordon and his circle (Bullock, Montoya, etc) saw its value, but others in and out of the GCPD hated it. They saw it as the police handing the city over to a vigilante. During No Man'sLand, Gordon tried to leave Gotham with his family but couldn't because no other city's police force was willing to take him on account of his perceived over-reliance on a man in a bat costume. Allying with Batman is a sore point among the GCPD, not everyone is fond of it, and I can't see them agreeing to strap Bat-Signals to all their blimps.