The L85A2 with a grip intrigues me

A grippod. Grip AND bipod. Fails at both. Not that you needed it on an L85 in the first place (though the Brits beg to differ with the carbine version).

Whether a soldier needs it and whether a soldier will slap it on their duty weapon are two criteria from sets that intersect nowhere

That's 100% true for civilians, but soldiers tend to only carry what they really need*.

*"What they really need" is affected both by #1 the number of days trying to scrape through the worst kind of terrain your CO managed to find with all the stuff you thought you might need, and #2 the number of precarious situations you had to deal with without the help of all the stuff you dropped after experiencing #1.