Ok - I see what you are trying to do...
I am really guessing here (I might be 100% wrong)... but I am trying to help anyway... so if you like, you could try the following...
In your skins/customer/home.tpl (might be skins1 directory - just check yours) - use the following code...
{if $page_name eq "home" && $main eq 'catalog'}
{include file="{$SkinDir}/{$shop_language}/homepage_content.html"}
{/if}
Note: at best this will only work to input a section of html on your homepage (and you will have to specify in the html width=100% etc., so that things do not get messy on different screen sizes)
i.e. you can not use an html page, to replace your homepage and expect anything to function as anything but an html page (so this, if it works, will only place the html content into the area specified).
Then set up a few directories on your server, under "skins" (or is it called "skins1" directory - check as I said) for each language you have, add a new "language" directory.
e.g. skins/US, skins/JP etc. and put the "homepage_content.html" page for each language, into the language code directory / folders...
Please note that I am really unsure if this will actually work (as I am a million miles away from being a programmer - lol)... but try if you like...
Perhaps others have a better idea...
Cheers - Asiaplay
PS: I am unsure if you can "include" an html file... you might have to include a "tpl" file for this to work at all...