LcLm give a very modest boost to the overall gamut. They are there essentially to smooth the highlight areas for up close viewing. The pale colored inks produce a less intense dot that's not as visible to the eye.
If smoothness is not essential, adding an OG to the mix will boost your gamut. Especially greens, oranges and red areas of the spectrum.
To get more colors out of your current ink set-up increase your number of passes and slow the machine down. You'll lay down more ink and give your current gamut a boost without expanding any one particular area. It might not open up the greens much, but you'll get an overall increase in tonal range that will definitely be visible in your images (with a new profile to take advantage of the increase of course.
How good a gamut is, is dependent on how much ink the media can hold. Resetting your ink limits both channel and total to take advantage of a media's particular thirst characteristics can produce some amazing gamut increases.
Using a top quality profiling package is essential too. Not all are created equal. I've seen a gamut increase with no other changes other than the profiling package create gamuts 30%+ larger than inferior profiling software. Use the maximum number of targets you can for best results.