"March with impunity" refers to Wanda, who can fly in, decrypt, fly out, while the battle is in progress. Since she won't attack on her turn, she is not subject to fire from opponents out-of-turn. I added the "picking the fight" thing because as it has been pointed out there's only one Wanda. Regardless, Parson could see where she'll be most useful.
Even if decryption wouldn't work on disputed hexes, there will be areas where GK will be able to kill everything on its start-of-turn attacks and that supposed limitation (we don't know anything either way, really) would not apply. We have seen Wanda uncroak after the golems killed in the tunnels, so the basic idea of this should work.
As for the money issue, one city at full production capacity is still less than a city and a village, each at full production capacity. The issue is not whether Stanley will have lots of money, the issue is whether Stanley will have so much money it becomes worhtless, as well as several, rapidly growing, villages/cities to pop units from. This surely must be quite a lot more relevant than you give it credit.
As for the problem, like many a time, is will and stomach. Which is what I've said for ages now, that I expect a split in the GK side.