Steinberg should make one! Something like Maschine mk3 or Akai MPC live, with a screen. It will be a game changer.
I’m loving GA5, standalone and especially with Cubase 10!
Hi
I just got a MASCHINE-Controller mikro mk3 for Xmas.
Is this hardware easily seen by Groove Agent 5 ? Hope it is « plug and play ». 
It´s plug and play just to certain extent… You will have to define the pads (“place” notes onto the pads). For example, with AKAI Mpc Mini the controller comes with a programming software where you define the notes on the pads. I believe that the Machine controller comes with a similar SW, too.