My general rule of thumb is don't permanently alter an import, especially one that's been banned. But your gun, your choice. What's your thought behind wanting to do this? Do you just want a shorter barrel? Alternatively, you could look at something like a Romanian M10, or a PSAK-104 or AK-E to get you a factory-built, SBR-ready AK with a shorter sight radius.
Downsides would include worsened accuracy if the chop and/or recrown doesn't go right, and the possibly of lessened resale value - any future buyers, especially Chinese AK buyers, generally aren't fans of Bubba'd guns.
If you do this, make sure it's all done right. I looked at a used AK a few years ago that was previously set up in SBR configuration. The genius owner removed it from the NFA registry by pinning and welding a muzzle device on his own. The only problem ... he drilled his hole for the pin all the way through the barrel and into the bore.