Sure, but then, you also need strict W^X memory protections, without exceptions (kernel included), since malware in memory of a device that doesn't often reboot is dangerous enough. For example, the very best malware for network devices never writes itself to disk even if possible, in order to avoid showing up in forensics. This already precludes most general purpose OSes and is still technically vulnerable to some convoluted return-to-X attacks that just swap data structure pointers around and use existing code to construct the malicious behavior, so I'd still feel better with a minimal trusted base even then.