That would make it analogous in a way to German ß.
The minute things show up in real orthographies the pressure to handle
ALL CAPS exists.
The question then is whether you'll find "SJ" or overlaid "S"/"J". Or
how a Swede would instinctively handle this, in the absence of an
example of a consistently applied rule.
(By the way, for those finding the German rule to write "SS"
unsatisfactory: It's hard to come by an actual minimal pair. And it's
not like capitalization is otherwise invertible – the capitalization
bits contain information as well, after all.)
Stephan
