i don't really agree of not to hang the guitars and the humidity thing here in singapore.
Humidity
first of all, get it right that even singapore being a small country we have certain places which are higher in humidity then others. Most of those places that are bad for guitars are actually where the richer people would stay. By saying most, i dun mean all. The common places i know that is bad for guitar are.. marine parade, bedok, pasir ris, jurong and etc.. basically along the coastline and bukit timah area where the vegetation is just next to you.
I stay in AMK(Ang Mo Kio) and have no problem hanging my guitars on my wall.I've done that for at least 6-7years and some of those guitars i rarely take it down to even strum. Dust is the only bad thing that will happen to my guitar and nothing else.
Warping Issue
If you tell me that by hanging the guitar it'll help on warping the neck, i strongly disagree. The amount of damage is infact greater when you buy stands like this
This is especially true when the guitar is supported at a tilted angle and not 100% straight. The support point will allow gravity to pull the middle part downwards over time. If i were to use this kinda stand, i'll normally adjust the neck support to the lowest possible height so as nt to add any possible stress. If you don't like wall hangers, i'll strongly go for this kinda guitar stand.
To save some spaces.
These are ok too because they don't stress the guitar on the weakest side but instead they rest it on the stronger side. Try bending your neck while playing this way, most probably you cant change the tune like you can doing the tommy emmanuel or billy sheehan way. But i don't recommend for long term usage.
So why is the wall hanger a good method to display but not warp you guitar neck? Simple, they hold at the top of the neck and the body is hang straight down. Gravity can't pull side ways and it's simply letting gravity to keep your guitar in the straight neck position.
I'm speaking from my experience with working with all these guitar stands and i've seen their results. Hope it helps.