Seems like newer version of VIX still isn't available as a separate download, I could find 1.17 in dowloads list but nothing newer.
In the end, I manually extracted files VIX32.cab, VIX64.cab from workstation 15 installation file, extracted those cabs and renamed files according to vix 1.17 existing files (compare file sizes and dll names in file details; and vix and vixd libraries are exact copies). Then I put them in same structure in Workstation-15.0.0 folder, and added workstation 15 strings from txt file (inside VIX32.cab) to vixwrapper-config.txt
Seems to be working - started my home web server with vmrun and -nogui, everything's working so far.
I didn't want to install full workstation package since I think it'll mess up my player installation.
Of course, I am still hoping for a separate download of VIX api...