Well any help?
By 'openers' I presume you want to edit .msh files on Mac? Well I'm sorry to disappoint, but there aren't any.
The only meagre hope lies in converting the .msh to a format that you can mess around with. However all such programs are also PC exclusive.
The only suggestions I can make is to either;
A: find a friendly PC modder with a lot of time to port things for you
B: Don't do A, because it's stupidly convoluted. The only proper way to do it is by partitioning a chunk of your Mac into a PC with bootcamp or whatever. Or buy a cheap PC.
This all depends on how desperate you are to open a .msh file.
tldr: no.
Well I tried to port the MSH Viewer with Wine and for some reason it doesn't load any models so that was a bust that's why I could use something that can open a MSH
Oh you only wish to view the models... Are you skinning or something? If so, you could go with option A and politely ask a PC user to test the skins for you.