The traditional way of composing the danish wovel 'å' and 'Å' uses 'a' and 'o', which surely is intuitive for non-danish speakers.
However, the danish 'å' is actually a combination of two 'a's, like the 'æ' is a combination of 'a' and 'e', and the 'ø' is a combination of 'o' and 'e'.
Combining 'o' and 'e' to form 'ø' is probably a bad idea, since there already is a more intuitive combination: 'œ'.
The digraphs in Vim and GNU Screen provide the combination of 'a' and 'a' to form 'å', and this doesn't seem to conflict with other combinations. I propose adding this as a default combination, as this would make transitioning from Vim and GNU Screen easier, and would be more intuitive for native danish speakers.