Another feature I would like to control via LS or the C-API is checking and setting the checkboxes on the replicator page. Indeed this information is stored in a $sitemaplist field. And yes it is not documented, though I am busy decyphering it!

apart from decyphering it, how would you go about modifying this field?

some basic stuff I noticed when I looked at it shows that for each replicator page entry there is a structure which consists of a section with a fixed length (72 bytes) and a section of variable length.

The third byte of the fixed sections shows how long the variable length section is.
This section contains things like database title, filepath and replica id.

And before I forget, the 47th byte in the fixed length section controls the 'Enabled for scheduled replication', 'Receive documents from server' and 'Send documents to server' flags on the basics tab of the replication settings dialog

enabled for scheduled replication(1) + send documents to server(2) + receive documents from server(4)

@2 (a late reaction) it will mean that you need to build the whole structure bit by bit. By the way, I stopped my work on this, because I was assigned to a different customer.