My arguement against 2 spaces and for 1 space is that 2 spaces is semantically wrong and 1 is semantically correct. We use a space to separate 2 words and a full stop (etc.) is used to indicate the end of a sentence. We don't need full stop and 2 spaces.
Now, traditionally, to increase readability, typographers used 1 and a half spaces after the end of a sentence. It looks pretty good and so someone decided that would be 2 on a monospace typewriter. However, our PCs are slightly (ish - not by much) more powerful than said typewriters and can work out when to use 1 and a half spaces if necessary.
Awfully convenient that the etc. happened to be in brackets then. I guess the previous sentence ends at the etc. when I don't put it in quotes and after then if I do.
But you should always use "i.e." because it's an abbreviation for two words. And I can't even think of a case that you wouldn't follow it with a comma (i.e., "i.e.,"), so that doesn't conflict with the ". " end-of-sentence pattern.
There are many style guides[0] that treat i.e., e.g. and the other Latin abbreviations specially in always punctuating them - it's rather rare to find someone talking about the former U.S.S.R., T.C.P. packets, or N.A.S.A.'s missions to the I.S.S. - to all intents & purposes, ie is the exception, not the rule. It's worth pointing out that i.e. is exceptionally difficult to type on a lot of mobile devices.
Now, traditionally, to increase readability, typographers used 1 and a half spaces after the end of a sentence. It looks pretty good and so someone decided that would be 2 on a monospace typewriter. However, our PCs are slightly (ish - not by much) more powerful than said typewriters and can work out when to use 1 and a half spaces if necessary.