Installing the GN drives will boost all their existing suit's performance, mainly in thrust power and GN powered weapons, as well as stealth. I'd imagine, but they'll need more than that to completely own the Gundams. Unlike Wing, I don't think they've mentioned anything about Gundanium, but the Gundams are obviously made of much tougher material compared to regular units. One thing though, how will they operate with GN particles pumping out of their backs? They won't be able to use thier normal suits without replacing all the equipment with something GN compatible, so I'd expect only our main characters to use these drives for now.
Now, about these rigged Solar Furnaces.....I think the answer may be in this ep already. We see Tieria has the power to cripple any machine that has links with Veda, possibly meaning any with GN drives. Now we have someone supposedly from CB distributing Solar Furnaces to the enemy....put the two together.....you get a suit with one huge weakness.