It appears that the reassembly API doesn't handle inserting "known middle" fragments (preferring them to be known consecutively). This appears to be at least one of the reasons the SCTP dissector does its own reassembly and why the new Bluetooth dissector from bug 7675 (
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7675) may need to do its own reassembly as well. Am I understanding the reassembly API correctly or am I just not being creative enough to understand how to represent a "known middle" fragment with the current API?