as far as i can tell, ~かれ is the imperative form of the カリ活用 of an -i adjective.

http://ja.wikipedia.org/wiki/形容詞

I think 遅かれ and 早かれ are old imperative inflections of 遅い and 早い. Certainly the mention of 遅かれ早かれ in the Kenkyusha 新和英中辞典 is under the 遅い entry. The Wikipedia page mentions かれ as imperative.
Anyone else throw light on this?

See below.

This submission is not about editing the above, rather it is about the meaning of "かれ" which follows "遅" and "早".

I wondered where "かれ" was derived from in order to give the resultant meaning. I searched around without success. I asked some Japanese people. Most told me not to bother about such things and just accept the translation. Some told me that it derived from "かれど（も）" or "かれば", but that did not seem to be wholly supported by some more research. Some told me that it was an old version of "にせよ". That makes some sense. One told me that according to their electronic dictionary, "かれ" was an old term which equalled "だから". That too would make sense. However, I cannot find that link.

If that last explanation were correct, then an entry for "かれ" with a simple link to "だから" may be helpful to a searcher. Maybe, also a link to "にせよ" would also help.

However, if your existing knowledge or search produces uncertainty, you may consider that it is not worth an entry. That is why I did not make a simple submission based upon my current information. At least, if you decide not to include it, I shall know that the majority of people to whom I spoke were basically correct.

I thought about this for a while. On balance I think I'll stick with just the rarer->more-common xref.