The Mk48 is/was not an act of war. As Ken points out, indications are that it simply won't cut it on extended ops.
However FN's "Minimi 7.62" is as robust as an M249, but not as robust as an M240. Point being the Minimi 7.62 was designed for dismounted operations.
I'm not sure there is actually much difference between the two Wilf. The 48 is made in the US, the standard in Belgium, both by FN. They weigh the same. The 48 has a different gasplug and (sturdier) bipod. Other than that they appear to be pretty much identical.

Your point on lighter weight guns for section/platoon level is well made I think. Keep the MAG 58 at coy.level or above, close to their SF kits with spare barrels etc. (and from there they can of course still be used in the light role when required.) For as far as weight is any indication of robustness, the 7.62 Mimini is not much lighter than the old L4 (agreed, mag fed). I don't think the L4 had any durability issues.