I'm wondering if they might not have gone the 25mm route using the research the US was doing into systems such as the XM-307 and XM-25.
The aim of the G11 was after all to minimise weight while maximising ammunition carried. The advanced 25mm ammo appears to do this admirably (although I'm sure there's glitches to work out).
I'm thinking they may have taken that a step further too and made it caseless given much of the chemistry was already done for the 4.7mm round.
Perhaps something like the Metal Storm GL could have been looked at.
http://world.guns.ru/grenade/austr/metal-storm-e.html
By today, it could have developed into an absolutely outstanding system.