Whatever the case, I think it helps greatly if you can get rid of the two hunters by Oguma early - say on their first or second chance they get a turn with a cavalier (likely Paola/Catria) holding a javelin in their range.
Chapter 7 is pretty ridiculous. I would normally face Ast(o)r(i)a/m's reinforcements in the open just outside the range of all the heroes boasting more than 20 AS and 30 attack, so my cavs can have fun with their broken move, but it's been way easier to lure them into the woods dominating the map since the open by the southwest cave spawns overpowered fire dragon(s?) I'd prefer to gang up on at the end while the northeast open is really small and awkward. It also lends my flyers a massive tactical advantage, especially since Paola's on the verge of promoting and can OHKO the obnoxious mages mixed into the reinforcements without orb fragments. Healers only having 2 move in woods, though.....bleh. Worse than knights' normal move.
So I tried your ch 4 strat. It's a nice strat, but it takes 2-3 turns longer than it would if you had warped marth north (12-13 instead of 9-10). Right now it's hard to tell whether a rescue charge or 2-3 less turn count is more valuable.
Chapter 9 is a lot more hardcore than I thought it was going to be. Most of the dragon knights rush you on the first turn, and like all the mages and Etzel on the next. My Marth's been having nice speed gains and still gets one-rounded by the slowest of the dragon knights - WTF (he can't double squat on the map either). At the same level, the developers raised their AS by like 5-6.
Emirzian: I only watched those videos up to chapter 7. I'm not going to spoil this mode for myself.
Paperblade's unit sucks, LOL. And he promoted not only the goddess that is Cat, but her early to cement the fail.
6x is over with quickly, but actually caught me off guard twice due to Caesar and Raddy. When they were the only mobile enemies left, both attacked my myrmidon Paola healing on a fort when each could have gone after sniper Sirius or armless Marth and dropped like flies (she didn't even have lady sword equipped, just lame iron). Never again, I swore. How foolish of their AI.
The four silver axe fighters are the most dangerous on the field by far and I eliminated them all on my first turn.