SD's response is correct. The JAA examiners take the view that weight neither affects VMCG nor VMCA, the FAA think it does. You should search tech log for this, there are are number of carefully written and technically correct responses in the archives.
To the second question, what would you do if you were VMCA or VMCG limited, one answer that BA used would be to reduce the thrust. The -500 TriStar fitted with RB21-524B4s had an option to pretend that the engines were only the lower thrust -22B models and use the VMCG values for that fit. It meant that, if you lost an engine on take-off, you couldn't increase thrust on the live engine but it produced the bizzarre situation where payload was increased by reducing thrust.