I downloaded a quake-style "Original Grenade Launcher" skin from gamebanana http://gamebanana.com/tf2/skins/119700
and found that in sv_pure 2 servers my GL viewmodel ended up like this.
after reading through the comments I found that removing this folder:
tf\model\c_models\c_grenadelauncher\
results in a constant center-held regular grenade launcher regardless of a server's pure setting. After that, I tried renaming the c_demoman_animations.mdl file that came with the skin and making a copy for each class and sticking them in the tf\model\c_models directory. This had mixed results. 99% failure, not counting that the demo's animations would obviously be applied to all weps rather than just the desired ones. I think it's because most classes' vanilla weps aren't c_models but v/w_models, and that the game seems very, very confused as to which of the demo's weapons is his primary and which is his secondary.
so basically, it seems there's a way we can have center-held viewmodels in league servers, which obviously has several advantages (more visibility than viewmodels on, no more shotgun jumps, quake vet circlejerking) and we just need someone to make the animation .mdls for it. I've contacted the uploader of the quake GL modeler about if this would really be possible and am awaiting a reply, but it already seems like this is well within the realm of possiblity to my uneducated self. So can it be done?