I thought points left on table was nice, as it was a downside for Fortifications, rather than an additional advantage for them (or at least for the Aegis). As was pointed out, though, most of the Fortifications can be killed, and the number of points which can be "hidden" this way is small.
That BFS mission was a good'un. Of course the BFS missions are NOVA-style (W/L), but can certainly be adapted for battle points.
The reason I feel like we shouldn't use both Big Guns and Scour in a 3 round event is because they're basically identical.
They're identical in mechanics, they are not at all identical in how they play out. Mostly because armies tend to favor either heavies or fast attack, and partly because heavies and fast attack usually behave completely differently (Fast attack being, y'know, fast).
I do not feel the 6 objectives is the essential element of either mission. I would feel free to drop that down to 5 and align it wiht a more standard Objectives mission.
Big Guns doesn't have six. It has D3+2.
While we're giving feedback on missions, I'm not a fan of multi-objective missions being fixed at 5. A range of 3-5, player-placed, is generally best, IMO.
For my money, the main reason not to use (at least not regularly) both Big Guns and Scouring in a 3-round tournament is that they're each only 1/6 of the standard missions. So having them both show up is doubling the intended frequency of the concept- making something other than Troops scoring.