I'd add the new 18m Jonkers JS-1 Revelation to that list. It'll come
as a jet sustainer and conventional self launcher as well, it would
definitely be on my short list. The Antares now comes in a dedicated
18m version as well, but only with a conventional Solo sustainer
engine as option. If I understand it correctly the 304S Shark comes
with a jet self launch option (not jet sustainer) and a conventional
Solo based sustainer option.

Markus