Hmmmmm...let's see. You can spend the cost + of a new gun in 'bits', and then spend a bunch of time removing and replacing parts back and forth....
In the end, it's more cost and aggravation than it's worth...
The 1911 platform is an absolute 'sweety' in 9MM...do yourself a favour and
just buy a dedicated 9MM, if that's what you want.
I have a Sig 226 in 40S&W and have a .357Sig barrel that just drops in..
takes 10 seconds..uses the same springs, ejector, mags, etc.
That's about as close to getting 'two guns in one' as it gets!