multiple main “index” pages–possible?

Here’s what I’m trying to do:

1) I use a straight index.php file as my template. I’d like to have a file called main.php in my root directory that is laid out differently and only displays one category.

2) I’d also like for the “*.php?p=234” to work on this other page.

At present, it doesn’t. I can get the page to display one category, but I want users to stick with the same template when they go to an entry page from this new main page.

Does this make sense?

I’m also thinking that my permalink structure might stop the “*.php?p=234” thing from working, although it works fine like this: “index.php?p=234” when the index.php is in the root, but when it’s anywhere else or looks like this: “anythingelse.php?p=234” it doesn’t work. If I turned off the permalinks, would this work?

Thanks in advance for any help/advice!!

Oh yeah and I was able to do this just fine in 1.2, but I hadn’t messed with my permalink structure at all at that point.