Mixed scaling for 1-4 interactions
Some forcefield like Glycam uses fudgeQQ and fudgeLJ as 1.0. However this forcefield supposed to be compatible with Amber family forcefileds. But in that case its not possible to use this combination in Gromacs because 1-4 mixed scaling not supported.
I think it can be implemented like this
1. make fudgeQQ and fudgeLJ arrays (changes mainly in topio)
2. attach fudgeQQ and fudgeLJ to atoms (need to modify format of ff*.itp files, may be need to add aditional section)
3. Make gromacs topio works with this arrays (changes in topio)
Another possible solution is to add possibility of stacking forcefields.