Modular cache subsystem

Hello everybody!
I'm very interested in creating a modular approach for cache management on Drupal.
Currently, the "cache system" is composed by three functions on includes/bootstrap.inc:

* cache_get($key)
* cache_set($cid, $data, $expire = CACHE_PERMANENT, $headers = NULL)
* cache_clear_all($cid = NULL, $wildcard = false)

Well, the first problem is that we may need caching right at the bootstrap time, and modules of /modules/ are not available at this time.
So, for me, the possible solutions are:

1) flag the cache manager (something like /modules/cache.module) as a bootstrap module and make it load right on the top of bootstrap
2) not having it as a module, but different .inc files (as it is with the database layer) that you can set up on the settings.php of the site which "cache driver" to use.

I want this because I would like to use memcached as caching system instead of using the database. Other people may like to use filesystem caches. I think that the best solution could be:

1) Having on sites/*/settings.php an entry like $cache_type = < "memcached" | "database" | "filesystem" > , defaulting to "database" (which is the current cache system). Something like:

// filesystem cache
//$cache_type = "filesystem";
//$cache_options['filesystem']['cachedir'] = 'cache';

// memcached cache
$cache_type = "memcached";
$cache_options['memcached']['servers'][0] = '10.0.0.12:11211:true:5:1:15'; // ip:port:persistent:weight:timeout:retry_interval
$cache_options['memcached']['servers'][1] = '10.0.0.13:11211:true:4:1:15'; // ip:port:persistent:weight:timeout:retry_interval

// default database cache
//$cache_type = "database";

2) Having a DRUPAL_BOOTSTRAP_CACHE (before DRUPAL_BOOTSTRAP_PAGE_CACHE) bootstrap stage, where the $cache_type would be loaded (basically just having its own implementation of the three functions above):

    // somewhere in includes/cache.inc

    $handler = "./includes/cache.$cache_type.inc";
    if (is_file($handler)) {
      include_once $handler;
      if (function_exists('cache_initialize')) {
         cache_initialize($cache_options[$cache_type]);
      }
    } else {
       // show a error message asking $cache_type to be fixed or commented
    }

And that's it. We should be able to use a "modular" cache system without problems (AFAIK).
I want to go ahead and develop this, but I'm skeptical about:
1) changing the core, since I will have to manually upgrade my code everytime a new drupal release is on the wild
2) there may be already something like that planned, and I'll waste my time

What you guys think about that?

Thanks
Daniel