Evil presence may be better than contaminated ground. They probably aren't dealing themselves all that much damage with the land, that having it cost only 1 may be better.
Maybe not, I could be wrong, but could be worth a try.
The field of ruin is sometimes different things; ghost quarter/tect edge, sometimes another colored source, etc.
Sideboard is also a bit of a pile, I've played different things. Cage obviously plays poorly with souls, but I felt like I wanted something else for coco. Sideboard could definitely be rebuilt though.
For affinity/lantern, pithing needle does a lot of work. We've got plenty of tools against affinity as well (zealous persecution, cheap removal, disenchant effects, etc) that dont have the same friendly fire as stony.
For 3 drops, little gideon has done some good work. Doesn't really work with copter, but he's a good stand alone threat.
The first list posted using mutavault had a bit on the high side as far as lands went, IIRC, as well as being a bit more all-in on smuggler's copter.
I agree that I'm not a huge fan of it either (my list doesn't play scooter, tho) because I'm usually really greedy on my mana bases, and colorless lands don't come cheap.
I feel like mot people aren't even running tidehollows.
I love the card, and its performed well for me, but I don't know if I'd want freebooter too.
Being a 1/2 is a lot worse, and while the flying is nice, its not terribly significant. Missing creatures is though.
If you play looter scooters and find yourself a bit low on fodder (not a fan of blade splicer, or something) freebooter could be worse I guess.
As for splashing red, not something I'd do. I haven't found a need for it, and I've never been happy with a build of mardu in modern. We have plenty of artifact destruction on color (though no mainboard) and while rebuying stuff is nice, I can live without it.
Having more consistent mana, as well as access to lands like ghost quarter/tec edge/field of ruin, mutavault, vault of the archangel, etc, feels much more valuable to me.
You could play more isolated chapels or fetid heaths if you wanted more duals. If you're playing push, I'd definitely go up to 6 fetches atleast though. 4 shocks is also a bit high, IMO.
For planeswalkers, sorin lord of innistrad is consistently underrated. He spits out tokens on his plus, and he gets lethal real quick with a lingering souls.
His ulti is also very realistic/threatening.
As for noncreature permanents, we kind of have to hope we can discard them
Luckily a top-decked moon is significantly less painful since we've likely had time to fetch some basics. Bridge can also theoretically be beaten with little gideon's ult milling them out (as lantern can struggle to beat resolved walkers, given that pithing needle won't help here.)
You'd almost certainly have to play an urborg at that point, but I feel thats too many colorless sources.
Tidehollow sculler becomes difficult, and likely painful, to cast on curve. Even liliana isnt as easy to cast as it should be.
Gideon might be better.
I really like old sorin, as spitting out a token every turn while going up, making permanent emblems, and an ultimate that is game swinging and reasonably easy to hit all on one card is pretty decent.
On top of that, I've already got 3 little gideons, and only 1 other sorin.
Ally of zendikar is definitely worth considering though.
IMO, pain seer is better than asylum seeker when you have copters. Sure, you can madness in seekers, but getting guarenteed card draw off pain seer is better overall. If you had lilianas, it might be a different story, though.
I don't own a fetid heath, but I would probably play one instead of the seventh fetch.
Otherwise, its not got anything crazy, just very heavy on discard and planeswalkers.
I feel that W/B has a lot of good planeswalkers to utilize, and spending the first couple turns ripping someones hand apart before slamming down a walker thats probably difficult to deal with, as they likely have little board presence, is our best plan.
Thus, the deck is built to maximize this outcome.
While having so much discard can often be a problem with topdecking it later on, we have so many powerful topdecks (walkers, souls, bob) to make up for this.