WordPress / mod_rewrite expert needed

Hello,

I am looking for someone who can help me modify my WordPress .htaccess file and customize the mod_rewrite directives to allow for more complex URLs and passing variables to PHP while maintaining WordPress "pretty permalink" functionality.

Something like this:

http://mydomain.com/hello-world

(would work like WP does by default with pretty permalinks enabled)

http://mydomain.com/varA/hello-world

(would trick WP into displaying the same "hello-world" post as above, but also would pass the "varA" string to PHP as a variable)

http://mydomain.com/varA/varB/hello-world

(would again trick WP into displaying the same "hello-world" post as above, but also would pass the "varA" and "varB" strings to PHP as variables)

to further clarify, the mod_rewrite code would be outputting something like this:

index.php?varA=$1&varB=$2

in which case I could easily grab those variables in php using:
$a = $_GET['varA'];
$b = $_GET['varB'];

Lastly, the new mod_rewrite directives would have to handle WordPress categories and tags which come in the form of:

http://mydomain.com/category/category1
http://mydomain,com/tag/sometag


BTW, the default WordPress mod_rewrite directives in my .htaccess file are:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]


Let me know if you think you can achieve this!

Thanks,
Devin

Further clarification:

I need a WordPress developer - the modifications should be done using best WordPress methods, to facilitate easy upgrading – i.e. using WordPress API hooks/filters/etc. as opposed to rough PHP code. I am using WP 3.2.1. Here's what I have tried so far:

I added the following mod_rewrite code to my .htaccess file:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(\w+)/(\w+)/ /index.php?st=$1&city=$2 [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(\w+)/ /index.php?st=$1 [L]

which kind of works. The variables are being passed, and PHP can grab them with:
$state = $_GET['st'];
$city = $_GET['city'];

The problem is that WP is getting confused by the URL and isn't finding the post. URL's like these:

http://epiclasers.com/state/city/hello-world
http://epiclasers.com/state/

are bringing up a page not found error. Also, when entering this URL:

http://epiclasers.com/state/hello-world

It redirects to: http:/epiclasers.com/hello-world
which then displays the post fine.

We need to modify the WP URL handling code to ignore the /state and /city parts of the URL without breaking URLs like:

http://epiclasers.com/category/category1
http://epiclasers.com/tag/tag1
http://epiclasers.com/category/category2/subcategory

etc.