The shell has always been awful. It is underpowered and overfeatured with a deeply crappy API. It is more like Windows 3.1 than any sane development environment.
The good news is that you don't have to implement initscripts as shell scripts. I recall at least one GNU/Linux distro that used Python for all its initscripts, for example. Really, as long as the "script" is executable, a SysVInit-based or BSD-rc-based system doesn't really care (unless it's doing something strange like calling a specific interpreter on each script - i.e. calling `sh /etc/rc.d/rc.*` or somesuch).
Actually, a FreeBSD or NetBSD rc system does indeed care, for that very reason. rc.d scripts are sourced by a /bin/sh shell, using the . command. See run_rc_script on the rc.subr(8) manual page for details. Ironically, it's daemontools and daemontools-like systems where what you say holds the most widely. Tools such as execline can be and are in practice used in "run" programs.
It doesn't look like OpenBSD has such a requirement (the start_daemon() routine in /etc/rc just calls each configured daemon's initscript as-is from /etc/rc.d without specifying sh or ksh to execute with); I had (incorrectly) assumed that this was a general BSDism rather than an OpenBSDism.
