It might not work the way you prefer using your favorite input method, but vim allows you to enter any utf-8 character, and even has mnemonic digraphs for many you are most likely to want. To get è, for example, in input mode just type <ctl>-k`e.
The point of my comment is that with an imap on <a-j>, you can't input the character ê because it will trigger the mapping. This includes option+i, e on OS X.
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Only problem with those imaps is that now you can't type ì, ë, ê, or è. Vim is pretty dumb about utf-8.
I'd also suggest using <C-o> instead of the <Esc>...i dance.
Edit: "The way [Vim] stores alt+letter in its input queue collides with UTF-8/Unicode handling" -- LeoNerd in freenode/#vim at 2013-04-15 15:22:29
I think I solved that problem quite elegantly :) However I still have a small TODO regarding printing from cygwin:
"Vim is pretty dumb about utf-8."
It might not work the way you prefer using your favorite input method, but vim allows you to enter any utf-8 character, and even has mnemonic digraphs for many you are most likely to want. To get è, for example, in input mode just type <ctl>-k`e.
Using the digraph will get around the insert-mode alt-key maps.
or `, delete, e if digraphs are activated (IIRC)
I code on a Macbook, and I actually use say... Option+i, e in order to get ê. That works inside Vim, too, I just found out.
Obviously not very helpful to people not on a Mac, but I don't have to go through Alt mappings at all.
The point of my comment is that with an imap on <a-j>, you can't input the character ê because it will trigger the mapping. This includes option+i, e on OS X.