Allows for custom UI in v21 by replacing profiles on GUIs rather than files.
This creates new profiles and keeps the old ones:
1) to follow rules of the Add-Ons forum
2) simply setting the bitmap variable on the profiles did not seem to work
KNOWN CONFLICTING MODS:-DrenDran's Advanced Eventing GUI (crash upon selecting input events)
-Nexus's Too Many Bricks Inventory (intense lag upon switching brick tabs/adding bricks to cart)
HOW TO USE:Place UI
you would normally put in base/client/ui/restofpath in
config/CustomUI/baseUI/restofpath. If you do not know how to do this, I cannot help you.
Another mostly untested feature of the mod is the ability to replace add-on profiles by placing them in
config/CustomUI/Add-OnUI/restofpath. This cannot replace bitmaps that are used on GuiBitmapstuff in Add-ons. This feature is completely unnecessary because there are no default add-ons to my knowledge that create profiles.
Proofs:

UI is Burnt Glass by SvennePOSSIBLE ISSUES: (ordered from most likely to least likely)
-Lag when opening GUIs for the first time each session.
-Default cursor showing sometimes.
-Some elements not replacing correctly on some things.
Download (Dropbox)If there are any issues with this mod, report them. If this mod should have never been posted, I'll just remove the download link and lock the topic.
Credits:
Clockturn - striReplace