Back with Mental Ray, it was possible to import 16k textures into Maya by converting .tiff into .map file format with imf_copy. As I understand, in Arnold an alternative for that process would be converting images into .tx files, but here I start encountering problems. Although using aiImage shader or place2dtexture node converts my 16k tiffs automatically into .tx files, I usually get fatal errors after while or Maya is simply unable to open and convert my images. And the render won't even start, because computer just runs out of memory, which is strange because I thought that .tx files should take care of these issues. So, if with mental ray it was possible to import 16k .map files, how it would be possible to do with Arnold? Also use .map file format?
Are you converting them via the Maketx command or the TX Manager? Maketx offers very fine level control of the process and for a map of that size it might make more sense to process it that way.