Although also being a small SOHO switch, may be Netgear GS-108T can suit your needs.
I want remove the initial staging step by allowing the installer to just plug the switch in and have the switch grab a config from a TFTP server noted by a DHCP option.
Not quite, it can download config from TFTP but only thru the web interface. No CLI. One thought: writing a script that the DHCP server would run to log into a switch and grab a config.
IGMP Snooping Dot1q VLAN tagging Preferably 8-ports
Check check check.
A decent set of rate limiting options (5/10/20Mbps)
Humm... it has 4, 10 and 20 Mbps. In the future you can also have 40M/60M/100M/200M/400M/1000M.
Extra bonus if it can also be PoE powered
Not from factory, but you might build a PoE power adapter to replace the wall adapter it comes with. The annoying thing about it's the "factory default" button which users love to press when there is an outage "to see if it works again". Cover it before sending such a unit to field. Rubens