I think quite a lot of Respighi's music would transcribe well for BB. However, one must remember that when the 70 year copyright period replaced the 50 year copyright period in 1996, Respighi's copyright 'resumed' until 2008 (so expect a plethora of Respighi- related brass band stuff then. Most, if not all of Howard Snell's arrangement of the complete PoR and Roman Festivals appeared when Respighi was out of copyright under the old 50 year rule (i.e. beween 1988-1996)). Though arrangements of copyright music appear and are granted by the copyright owners, some estates and copyright owners can be a bit choosy, which is why there's precious little brass band arrangements of the works of Richard Strauss, Kurt Weill, Maurice Ravel (who also went out of copyright and came back in) and I believe, Ottorino Respighi.
I'm not putting on my 'copyright' cap necessarily, merely explaining a few 'situations' from my own experience as an arranger and PRS employee! ;-)