A composite picc will be fine outside. It's basically plastic, so weather isn't going to affect it like wood. See if you can find a model with both head joints, and get the best of both worlds metal/woodish. Check craigslist to see if there's any deals. Also look into WWBW's composite picc--I've never played one, but I have heard good things about it. Not the greatest horn, but a nice decent player.
Although honestly, there is absolutely no reason you can't play a metal picc inside. I played the piece of crap Artley for years. I still play my silver Gemi for band, even for our few indoor concerts. It depends on the song, if I play the wood or the silver. For example, the folk songs I used wood; the Journey medley is on silver. Our director (who is very outspoken) has never once commented about me on metal. And our resident professional composer insists I play my silver--he prefers its sound over the wood's.
Really, it's all about control, rather than what the instrument's made of.
1975 Gemeinhardt M2 in chrome nickel
1982 Armstrong 80
2006 Yamaha 584
1978 Artley piece of crap 15 P
1982 Gemeinhardt 4S
1980s (?) Armstrong all wood (no model)
2006 Jupiter di Medici G0199
Plus many many flute-cousins....