[…] consultation with an experienced editor to guide you through making your own trailer?
I was thinking about meeting for a 30 min free consultation and then, if you decide it works for you, charging an hourly fee (around 40 Euro/h) to help devs with editing their trailers, […]
your role in the process is probably best specified as the driver of the game, unless your client already has enough play videos for the clips that the trailer must include. your external perspective as, ideally, someone who has not played the game yet, is helpful for generating the clips, and not only critising the trailer’s storytelling, than that of studio members who are already more familiar with the product being advertised than the target audience.
I have deliberately not commented on your proposed billing structure; that remains between you and your clients.