1: re: Improved Sensors and Active Probe. The best (active probe) should win out, rather than their being cumulative. Each entry should get a * mark added to them in errata.
2: The "Playing area battlefield" is the exact area you used in a prior game. If that happens to be multiple mapsheets or 1, either way, it's the playing area battlefield. Likewise in space, whatever area you had the game in, that's the "Playing area battlefield"
3: Anything that is defined as a unit in gameplay can take part in SAR.
4. First, the modifiers indicated should apply to the dice roll, which'd make it harder to get to 8+. We'll fix that and inverse the modifiers in the table. The intent is that each individual unit participating in SAR rolls for each individual MechWarrior, vehicle crew, escape pod, or lifeboat.
Example: 3 units tasked to do SAR. Unit One has a Beagle probe, Unit Two is a VTOL without a Probe, and Unit Three is a regular ground vehicle. Two hostile MechWarriors and one hostile vehicle crew have gone to ground.
Target number is 8.
Day 1:
Unit One: -4 (unit has gone to ground, day 1), +2 from the Probe, net -2 modifier to the roll.
Unit Two: -4 (unit has gone to ground, day 1), +1 for being a VTOL, net -3 modifier to the roll.
Unit Three: -4 (unit has gone to ground, day 1), and nothing else.
(Again, note that I'm flipping the modifiers on p.46)