Good question.
I guess in theory it may be possible but that is based on the simple rule of thumb that the host and scion must be compatible. Considering that a satsuki is from the Genus rhododendron and of course a rhododendron is also from the Genus rhododendron it meets that requirement. I do not know if it matters greatly that they are each from separate subgenus.
According to the The Grafter's Handbook by RJ Garner "the botanist classification only serves as a rough guide to compatibility, for it is founded upon the reproductive characters, and experienced grafters have learnt that this is not a reliable guide." Garner goes on to discuss in great detail how permanent unions have been established across one Genus to another, however it is uncommon. Incompatible unions are the distinct failure to unite of a mechanically sound union.
Great concept. If you know how to graft why don't you give it a try? There is plenty of information out there on how to graft and for the most part the tools and supplies are inexpensive. If I were to attempt this I believe I would attempt a thread graft. This seems to be the typical way that branches are added on an azalea and it would provide cambium contact while the donor plant sustained the scion. After a season or two the branch could be severed from the donor plant if the exit looks healed.
I say go for it - and keep us posted.