The breakage problem is interesting. Right now, a.b parses just fine, so existing code will break when this is turned on. And that is an issue as people often turn extensions on per project, but it's also something a code formatter may be able to fix.

(Hopefully britanny will get an update to handle this correctly!)

They could, In Theory, rename the composition operator selectively when this language extension is enabled. That'd mean Prelude has to change what operators it exports depending on what extensions are enabled, which would be horribly magical.