Hmm, you'd have to modify the .sht and maybe swap .eft's.
Though I know you can do a lot with the MATL chunk inside the .sht.
Basically, the whole chunk is nothing but reversed floats, the lower they are (meaning 0), the less reflective/shine it has, the higher it goes, the more it'll shine and reflect. How and to what extent, I'm still unclear about, I also don't know which value does what exactly, but missed around with it in the past few days, while I'm writing a .sht editor, which I'll release with my 'toolkit' in the next few days. MATL editing can easily be done without any fancy tool though, just need to hex edit or do it in TreExplorer.
Just remember, they're reversed floats, so 3F 80 00 00 = 00 00 80 3F in SWG.