The game GW puts out is not intended to be a serious tournament game.
This statement, which Benjamin has also used, is used to basically throw out all the all the changes GW has made for 6th, just do it your own way, which usually means "the way we have always done it", which winds up being a some hodgepodge of 5th, 6th, maybe even a little 4th (when were table quarters last in the actual book?), and generally don't work as well as if we had just used the rules without messing with them.
As much as we make fun of GW, quite justifiably, I think they are probably better at designing missions than you, me, or any of us are, or at least they have spent more time at it. Worse, some things are meant to counter balance other things: first blood is meant to counter the advantage of going second for objectives, and when you take it out because frankly, you don't like it or it isn't advantages to your army, your're messing with the balance of things.
I'm not in any way saying that the GW 6th ed missions are flawless...I'm specifically doubting the ability of any of us to do better. Certainly not without trying it their way first, and extensive playtesting with veteran players.
1. Yes, "should be as much like the 6th ed missions in the BRB as possible", I thought that was clear
2. Yes, I want to mandate a percentage, at least on average. These are randomly rolled in BRB 1/3 of the time. Fast Attack and Heavies are meant to be able to score objectives 1/3 of the time each, one of those two are meant to be able to score 2/3 of the time total, only troops 1/3 of the time. Presumably, it will help fight spam.
3. I wouldn't say "minimal", I'd say "secondary". They're meant to break what would be other wise ties.
4. There are at least 4 things wrong with spearhead: Minimum separation is less than 24" (which I'm sure Tyranids love but is not good for newbie players), It eliminates the possibility of tactics such as a "denied flank", It limits greatly the possibly sight lines of a gunline army (should you want to play one), and for a truly Horde army it's jsut crowded -- you have less than 25% (20%?) of the board to deply on, rather than the 33% as in all the 6th ed deployments.
Spearhead is bad and should not be used5. Again, percentages are derived from the BRB. I'm less picky about this than I am about it witht he shrouding and Big Guns never Tire, those really need to 1/3 each.
6. Yayyyyyy, we Agree! This zero zum thing might be the most important one to me.