Chaining Two Different Hash Types
#1
Is it possible to chain two different hash types together? 

I've got a known algorithm, salt and sha-1 hash as follows:

sha1[$salt.sha1($salt.sha1($pass))]

Which I could theoretically implement if I could chain the following two types:

4520
sha1($salt.sha1($pass))

120
sha1($salt.$pass)


Where password guesses would flow like --> 4520 --> 120

It seems like a no-brainer to be able to chain or iterate on some raw types. Am I missing something--is this feature already available?
#2
This feature is not available and, believe it or not, is not easily implemented.