A lot of the complaints around here concern unsupported devices. Wouldn't it be nice to give the diehard gadget freak a way to manually add device codes that aren't in ROM? This could take the form of a PC connection with download software, or (follow me) the equivalent of "magic codes" for DEVICE KEYS rather than functions.
Tricky, of course, since manufacturers may use different data formats and IR carrier frequencies, but AFAIK there are a finite number of variations.
You would then have to manually assign every function key using EFC's, so a LOT of memory would be required for such a remote.
And of course, if you have the original remote, it's a lot easier to use a learning remote to duplicate it instead...