There is a reason that most people don't use dynamic hair, as you have discovered.  It is an idea that isn't quite there yet.

There isn't a lot of truly great free hair.  The free hair that I like is by kozoboro & can be downloaded at www.digitalbabes2.com.  When buying hair, look for what is most versitle.  I would recommend hair by AprilYSH over at DAZ.  Most of the hair fits all of the DAZ characters.  Another good hair maker at DAZ is Neftis.  Here at Rendo I'd recommend 3Ddreams hair, it fits most characters & plenty of free fits are available.  Netherworks studios sells a hair conversion system that I have had good results with.  Right now they are on sale at 30% off.

Back to V4.  There are many people who really, really don't like how DAZ is working the V4 figure because of things like hidden dials.  There are some scripts in the Freebie section here at DAZ that will unhide those dials.  Of course, those dials may be hidden for a reason.

Getting rid of the purple bra is simply changing the texture of the mesh.  If the V4 set you bought did not include any, there are plenty of free ones here at the renderosity freebie section.  (No, I don't get a commission, I have just found a lot of good things here.)  If you look under morphs & textures there you will find over 250 characters, textures, morphs etc for your V4.  The clothing section as over 600 items, so there is plenty to start with.  Granted they are not as good as say renapd's stuff, but it is a good place to start.