Hey there,
I see you're looking for somebody who has knowledge of bigbluebutton frontend html5 client customization I understand exactly what you're looking for, I have an expertise in BigBlueButton development, configuration, customization, Client Layout design and development, HTML 5 Client Customization, Load balancing of multiple BigBlueButton servers.
i have worked BBB and php with iframe based integration. let me know if you want a demo of it.
You did a good job of explaining the role, but just curious - What kind of modifications you want, just iframe integration or something else ?