I am personally happy with absolutely trash audio quality when listening to podcasts, and frequently skip music, but have noticed many podcast producers will use high CBR* or overly high quality VBR MP3 audio and often justify it because they have to run with high bitrates for their music to sound good.
Obviously encoders have continuously improved overtime, but it seems like it would be an absolute no-brainer to be able to provide hints to an MP3 encoder that different regions of a file should be encoded with different quality levels. In most cases that would be something that could be left completely alone encode to encode- your intro song is 2:30 and your outro is 1:45, so you would just have it as part of your encoding options that you would have higher quality encoding for those regions and lower quality for the rest of the file. On the other hand, if you did have a show with one or two audio intermissions in the middle, you could still specify the specific parts within the file that needed higher quality audio and specify that those should have higher quality too.
Either way, you get guaranteed quality while potentially still saving on file size.
Is this something that is commonly available in any MPe encoder? It seems like a no-brainer.
* the other argument against VBR MP3 and other formats for podcasts is often related to problems with seeking in VBR or other files, which is reasonable enough