This has been suggested before, but the beauty of the ROM is that loading all your programs there does not take up any additional usable space. Some of those programs i agree with you on though as i've removed the MSN packages from the ROMs i make. I tried removing WMP, but is a core OS feature and afterwards i could not play music even with TCPMP. The way I see it you can still add any programs you want to after the rom build. If you still want a slim ROM though try downloading a kitchen and taking out some of the OEM packages that you don't like.
Edit: As an example the current rom i'm using which was developed with the 3.5 kitchen (
ftp://up.ppcgeeks.com/Apache/ImCoKeM...int_nk.nbf.zip ) currently has 36.06 mb free storage mem and 29.45 free program mem.