I have no idea how many sorcerers may have collaborated to do whatever to Eschelon, when this occurred (or if it needs ongoing, possibly "expensive" maintenance), or if it's partially or wholly some effect from pre-sorcerer times (when nanotechnology may have indeed been spammed more heavily). Many nations today have aircraft carriers (which can cost billions of dollars each) and other super-expensive things, so even if something was "possible" it can still be inaccessible to Vennice for financial reasons, which is part of what I've been saying. By the way, the next page says the floating rocks are clouds, not rocks. ;p
Maytag's arm replacement was "mirroring" in your link. Good luck mirroring wings or genitals you don't have or that you want changed. It seems to come back to the idea that restoring a default is easier (although mirroring being copying with a minor twist makes it even more basic, since it would seem that if Maytag lost both arms she may have been fucked), like one would think it would be in a story. In fact since it's not based on DNA this is a bit difficult to make work for random body part choices...good luck mirroring some random wing or genitals that aren't yours in the first place and having your body not reject it. And even if you didn't reject it there would be the question of sensing and controlling the new body part properly...perhaps not so much of an issue with mirrored arms, but extras like wings or swaps of genitals may not be easy at all to make work as though they were your own since birth. So we can easily be back to no luck for randoms like Vennice (perhaps Vennice is wealthy or a powerful sorceress or has such friends, but I have to assume not until otherwise is proven).
Anyway, calling it "easy" is relative. Clearly that location was well set up to do that, but if Maytag didn't luck into getting such help how "easy" might it have been to find and purchase it? Obviously healing is not "easy" in some areas, where "easy" should mean cheap, not "we're in the best area with the most sorcerers and specifically have a set up for this and have done it over and over to the point where we can reliably do it well". Basically, a surgeon in a hospital might call some operation "easy", but is it cheap? ("Free" healthcare just obscures the cost rather than actually lowering it, to be clear.) If you aren't relatively wealthy (let's say you're a random peasant such as might exist in Flipside or our third world) what are your chances of purchasing this? Vennice might not be a random peasant, but if she wants something better than mirroring an arm she already has one of she might be out of luck, as the price would normally be higher, since it would probably be harder than "easy", and "easy" very probably doesn't mean cheap.
I see no evidence law enforcement is doing much of anything. Of course if you looked and acted like a monster they'd normally act, but if you looked "weird" but didn't do anything is there a reason to believe they'd do anything? And of course one has to consider where one is...perhaps the knights would be very proactive, but as I recall they don't rule very much of the total land in Flipside.