Transmission gear rebuild

Here is something i have never run into before so looking for information.

I have a transmission that i forgot to add trans fluid into the trans and drove for a bunch of miles.
Now the gear welded to the mainshaft. So i cut the mainshaft and bored it out.
I have another mainshaft.

Now here is where it gets interesting.

Could i take that gear and buildup the inner hole with 7018 welding rod then remachine to the correct diameter ?

I have all the tooling and a machine shop. I have just never ran into this issue before.