liggghts and implicit time integration

Hello,
Is there a way implement a particular force exerted from the fluid side on the particle to be integrated using implicit time integration, ASIDE from the dragforce. It seems there is a possibility to integrate ONLY the drag force implicitly:
https://github.com/CFDEMproject/LIGGGHTS-PUBLIC/blob/master/src/fix_cfd_...

I really need to take this particular fluid force (which is just a value passed on to liggghts say similar to the pressure gradient force) implicitly for stability reasons else I have to use a much smaller time step for no reason. I would very much appreciate your input on how to proceed and the steps to follow. It was quite difficult to see the steps from the fix_cfd_coupling_force_implicit specially given my rusty C++ knowledge. Furthermore, this should be much simpler than the dragforce implementation as the force value already exists.

Again I really appreciate your help on this.

Thanks
Ali