I think it is highly unlikely they are a straight swap. Also Breitling know what they are doing when choosing crown size and style to suit a case, I don't think it would look better, in fact, I'd bet on it looking rather odd.

 

In most cases you will find it will screw right on ...however the stem may need to be replaced as I'd bet a larger crown will have more thread inside it, you could shim this with a slither of solder to pack it out (old watch makers trick aparently?) however I found a new stem to be far less hassle as if you get it wrong the crown maybe unusable as it's hard to get out again without heating it up.

I'm all for making a watch what ever you want, I'm not a fan of Breitlings to start with though.
... if it was a Bregeut I'd probally talk you out of it and start a petition and stand in the rain in car parks asking people to sign it but at the end of the day it's your watch and your taste.

Incidently my old 21 jewel AccuristI replaced the crown on becase it was almost bald with no knuling on it, found a crown the right size and thinking about putting a seiko presage crown on it, not a full onion but thought I might be able to actually grip it with my bananna fingers

 

If it were a Breguet I would not consider messing with it!