Yes, I don't have N900 so N8x0 and 770 are my preferred devices :-)
Official ScummVM package (the one available at scummvm.org site) adheres to rules set by ScummVM developers. AFAIK the SCI engine is currently disabled in official build since it is not out of beta, see http://wiki.scummvm.org/index.php/Engines . Many engines live like that for a long time. Once it is good enough it is enabled with a big fanfare in some release. I am not sure about stability of SCI engine but for build in Maemo extras I guess we can have extra beta engines enabled if at least some games are completable for such engines. Or maybe it would be better to make available some unstable scummvm package with all such engines enabled.