i have good knowledge in Visual Basic, and i considered making one of those, but the idea stayed for like a whole 30 seconds. I dont have the time to make the whole thing. as for your idea for buying .OCXs for the layout, its a waste of money. The best layouts are made without those annoying ActiveX controls.
Definitely put .MP4 conversion from .ati, .mpeg, .wmv, and try to include .rm because i havent seen any of them yet and i have some video in Real format that i wanna convert. also, if you can import compressed .MP4s for further compression, that would be a must have app.
for music, put in an mp3 encoder and if possible an ATRAC3 and ATRAC3plus encoders becuase that format doubles the amount of music you can put on ur MS without losing quality.
for pics, put in a jpeg converter, which is easy
for games and gamesaves, make it able to transfer PBPs (EBOOTs) as well as gamesaves.
if you need any help with the programming part, PM me and i'll try to help as much as possible. good luck!