I changed from the Yamaha handguards in the autumn to Barkbusters, not because the Yamaha ones weren't any good as physical protection (they were fine), but for better weather protection. I opted for the standard BB plastics which work much better than the Yamaha jobbies, but for a few quid more I wish I'd gone for the Storm plastics for total protection from the elements. The plastics are really easy to change though.
Regarding the weights, the dedicated backbone kit for the Z now includes bar end weights (that go between bar and guard) and fits without mods. They are about half the mass of the OE weights though and vibrated a little more, so I also fitted the optional BB outer weights, which brings the total mass up to the same as OE. No more vibes.
Tenere backbone kit
Storm hand shields
External additional weights