security risks in using dynamic .htaccess ?

[something else]

Below is an example of how to change your Status Code 404 page to 3 different random pages:
something-else1.php, something-else2.php, something-else3.php

<?php
$fh = fopen('.htaccess', 'w') or die('cant open file');
fwrite($fh, 'ErrorDocument 404 /something-else'.rand(3).'.php');
fclose($fh);
?>

I was wanting to using use it with modrewrite to make a dynamic set of rules which will be wrote to .htaccess for different users of the site but is it to much of a security risk?
and also will this lag the server?

[morse]

What if one user is opening some page on server while other users action has initiated a .htaccess file writing. Would htaccess be available from the server during that transition period? What would happen ? :p

Added after 2 minutes:

Also, Instead of going all the way to edit htaccess, why not make a certain 404 page and use random values to show up a dynamic random end result? just my thought

[something else]

yeah good point 2 users could be using .htaccess at same time so it could mess up ...... the 404 page was just a quick example to make sure it works ....
but you could use it for things like banning an ip range etc....

the security flaw that i was most worried about is if someone manages to hack it and turn .php extension off making your script visible to everyone :/

normally i would be able to use modrewrite to make a set of rules but the server that the script is on has very limited mod rewrite allowed and this is the only way i can think to get around it.