MCS itself is perfectly fine running w/o root privileges except a couple of things:
ExeMgr, WriteEngine and PrimProc raise a number of open file descriptors so systemd units must contain LimitNOFILE=65536.
There are a number of directories that must have appropriate access modes and owners. Here is the list of related commands I run to get MCS working under an arbitrary user.
There is a relevant article on installing MCS under non-root user.
The upgrade from 1.2/4 to 1.5 must be tested.