Yeh, I have a Magpul MOE handgaurd but you've still got the FSP weight up front, a free float rail that is designed light - like the Fortis or NOVESKE NSR for example - means any weight is kept closer the pistol grip.
A Bocca isn't really much lighter than the standard TM RAS system, just a different mounting interface.
Don't get me wrong a polymer handgaurd def saves weight.
I have a proper Magpul (not PTS) one available 2nd hand if you did want the easiest route