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@Ian-Steele the boot time for an Omega is effected by a range of factors, number of modules loaded, services to be started, network connection etc., sd card read, file system check etc. My Pi3 is no faster.
Adding a script to rc.local I would consider a bit of a hack, hotplug was designed for the task you asked about, but actually hotplug is deprecated in favor of udev but I haven't tried udev on Omega/OpenWrt.