It's important for me to understand what "bloatware" you're talking about. Did you get your phone from a cell provider? If so, they are notorious for pre-installing and re-installing bloatware... er, "featured content" - Verizon being one of the worst offenders. Most of it (games and their own VZ garbage) can generally be uninstalled or disabled. It's one of the main reasons I always buy my phone unlocked, straight from Samsung.
Here's the downside to disabling updates:
Android is a complex operating system and there are some pretty naughty people out there in Internet Land, looking for vulnerabilities in the Android code they can exploit. There are also good guys trying to do the same thing, so they can alert Google. It's a race: when the good guys find a problem, a security patch is then sent out to manufacturers and carriers to close that vulnerability. Unless you never get online with your smartphone, either on Wi-Fi or cellular data, those are really important security patches that are included in the regular updates that go out. If you deliberately disable updates because you don't want to deal with bloatware or OS features you don't need, it's only a matter of time before your phone is so out of date that it becomes a target for the naughty guys. Anything from keyloggers to a complete takeover of the device is possible. There may be better ways to solve your problem.