SEO multi language

[ServWise.com]

Some time ago (11 years) I created a system to make WHMCS fully Search engine friendly using URL rewriting. That was using version 4/5 of WHMCS, it allows you to have nice looking URLS and most importantly it allows search engines to properly index all multi language content on the site. Well I put of upgrading for about 5 years, in fact I attempted to upgrade a number of times (And paid for the upgrade subscription each time) but never managed due to the substantial changes in the newer versions. I am now forcing myself to complete the upgrade and one of the final issues I am seeing is again to do with rewriting.

Unfortunately in v7.8 WHMCS's index.php no longer seems to allow you to rewrite to it, for example I would like to rewrite /en/, /it/ and /es/ to my /home/ folder where WHMCS is actually installed,  I then force ?language= to the end of the source urls so that WHMCS is forced to show a specific language for a specific URL. This works for all pages except for the root index.php, likely because of the new "Friendly URL" system WHMCS has implemented.

So what I am asking is if anyone here has any insight into how we can rewrite the index.php file without getting a 404 error page?

I have opened feature request as the language issue is something that should have been fixed internally a long time ago in WHMCS.