A New, Future-Proofable Archive Format

I've been dealing with different archive formats recently, and I'm a little bummed that none of them do everything I want. So I've been kicking around the idea of an archive format that is scalable to future algorithms, can be optimized at pack-time for what is stored, and can be updated with more advanced decompression algorithms without needing to update the client. What I've come up with so far is embedding a small subset of a programming language into the archive itself.

Examples:

Text files can be compressed with the same LZxx algorithms today

WAV files can be compressed as FLAC files, and decompressed on the fly as needed

Bitmaps can be compressed any number of ways(PNG/JP2/...)

One hurdle is making the decompression algorithm small enough for this to be effective. That said, for small files, a smaller but less efficient decompressor may be included to keep the total filesize still small.

Future proofing is intrinsic - when an archive is packed, it contains the algorithms used to compress it, so any new compression algorithms will work fine on old implementations.

Security concerns - each archive contains one or more programs running on the user's machine. This is where exposing only a subset of normal OS bindings comes in - the program gets access to read the compressed data block, ability to read/free memory, the ability to write to the output buffer, and of course entry/exit points for open/close/read/seek.