While it may not solve all your problems, I noticed there's a plugin that optimizes how Find transmits asset data (images, docs etc) when indexing. The plugin reduces the amount of data sent between client and server when indexing, which might be a good thing in any case.
More here: http://world.episerver.com/blogs/viktor-sahlstrom/dates/2016/1/improving-search-relevancy-for-attachments/
Thank you for the tip. Looks like it might have an impact. I will definitely look into it.
In our scenario the customer pays for a specific band width. Unfortunately there is no actual physical limit to this. So he/she can actually use more, but have to pay extra for it if it occurs over a longer period of time or very often. When Find sends it index to Episerver it uses all the bandwith available, meaning that it exceeds the limit that the customer has payed for.
The question is; is it possible to send the index in specific chunks or in other way limit how it is transmitted?