#1
I have an early 80's "Harmony" strat that I have customized to a degree. I love it, but the neck is a bit narrow for me.
Would it be worth it to try and fit a wider neck? I have to take some measurements to see how much actually has to change on it. I know the string spacing on the bridge is narrower than say a Fender spec, so I may want to change that too. I may put a fixed bridge on it since I don't use the trem at all, so I will probably have to fill the cavity for the trem block, but I don't think I would do anything with the spring cavity.
I have modified neck pockets before with a measure of success, and I would like to try this.

Do you think it would work?
#2
I've put Fender replacement strat necks on Lotus and Harmony copies before. The pocket fits just fine in most cases. Make sure you don't get one with the pre-drilled neck holes, you'll want to do that yourself.

If you want fatter, take a look at the 59' profile Strat neck. It's pretty chunky.