you could make it semi. but for all the money and work to do that. you could get a spyder. if there's a way to improve velocity then it will be by getting new springs. htere isn't a way to make it easier to pump either (not cheap at least) you should probably just get a new gun. a cheap pirahna or spyder. see if there is a paitnball shop somewhere not to far. if you want to increase velocity, they would know how (if it's possible) pretty much anything you could get for it would cost the same as a cheap semi auto. even the only BE barrel.
Teh best upgrade to a BE is to sell it. That is if you're wanting to compete. For the money and time it would take to upgrade it, you could just get a piranha or spyder. I'd suggest a piranha, as you can find them for under 80 bucks on the net...
Brass eagles are known to break very easily.. I'd suggest finding a new marker.
I don't suggest selling it. You would only get a couple of dollars for the hassle anyways. Clean it up real nice and pack it away for later memories. Personally I wish I hadn't thrown my old talon away since I've got a lot of fond memories of using it in my early paintball days.
If it was me i would find a newbie, sell it to him. Thats what I did with my stingray I came away 40 dollars richer. But only after that I relized it was better then my pirhanna. Then the kid broke it. Thats all behind me now. Now I roll with a cocker.