I'm assuming you still want the domain itself to redirect, but would like to do other stuff in the other directories?
Ex: domain.com/ redirects elsewhere, but you can still have something like domain.com/images and view them there?
If so, you could switch that domain back to full hosting, then just create an index.php page that does a 301 redirect to where it currently points.
Create an index.Php and get rid of other indexes (htm, html, etc...).
This is what should be in index.php:
header("HTTP/1.1 301 Moved Permanently");
Is that what you mean? If you do that, index.php will redirect to the other domain, but anything else can be called from where ever you put it.
If you simply leave the domain as a redirect, then you can't call other files from it. But there's no reason to leave it as a redirect, since you have unlimited fully hosted domains.
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