So here's what I did to get somewhat suitable controls with PS4 controller in the current released version.
When you start the game in the settings window select input settings. For all the inputs double click the entries and set it to what you prefer.
Then for 'Digital Aim' make the secondary the R1 button (or L1 if you prefer).
Then for 'Analogue Aim' you need to set it to some analogue input that is 0 when not pressed. On the PS4 controller I went with the D-Pad Y-axis (up on the d-pad). Since I use the L-stick for movement, the d-pad doesn't do anything.