Great, so if you have contact with the developer of MyVesta, you can ask him what are the most compromising functions of PHP and other important security implementations, plus it would be great if you join forces to work the two communities on the same project. In myvesta’s github comes a line that I think are the disabling functions and I put them here for you to value disabling them too.
+disable_functions = pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wifcontinued,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_get_handler,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority,pcntl_async_signals,exec,system,passthru,shell_exec,proc_open,popen