I'm a music publisher and label owner in the Uk.
I've released about 30 albums for client i've recorded and published since 2004.
All of the tracks on the albums were registered with PRS/MCPS and PPL.
I never submitted the tracks to any music libraries but they have all been used on radio and TV stations worldwide, so as the publisher i recieve the royalty income and then i distribute the agreed prcentages to the clients that have had their music used.
I also provided CD's to CD Baby pretty much from the beginning of release time and have sold quite a few hard copies, of course now with the era of downloads, the hard copies aren't in demand these days, so i now recieve a quarterly royalty income statements to my email address, whereas several years ago i'd recieve the statements in paper format.
One bit of advice that i was given in the early days of distributing from a TV producer, was when the promo copies were posted to to the various media for review, the advice was when sending them to the TV and Radio stations, make sure that instrumental versions were included, so they could be used as idents, background, etc.
This made a hell of a difference to royalty income, due mostly to the mechanical usage on TV.
What i realised over the years, was that you don't really know where the music is going to end up.
A six track EP i released in the Welsh language (i live in North Wales, UK), became record of the week on an Italian radio station, so it can be an amazing business.
I would certainly consider startinga publishing company, if you intend submitting the music of the bands you are in, as you state.
I'm not sure what the situation is in the US but here in the UK, it's very unlikely that radio and TV stations will take the submissions seriously, unless they have been submitted by a publisher.
I have two record labels, one for the Welsh language releases and the other one for everything else.
A music publisher can have several labels under the publishing umbrella, depending on how many genres of music is intended for release.
So i would seriously consider taking on the role of a publisher and a label owner, it tends to keep everything under control, plus you have the added kudos of owning/holding the copyright via the publishing company.
Maybe do a touch of checking out what i've mentioned online and see how things are for a similar business in the US.
Any other questions, just ask.
Take care.