I'm not sure how much research you've put in to this but there are some stable GPS ROMs out there that include the standard boot loading screen (HTC) and not the Swedish Chef.
Go here -
http://forum.ppcgeeks.com/showthread.php?t=25335
Follow the instructions. Install the Sprint Test ROM then flash with the OMJ.WM6.1.GPS.OEM.Sprint.exe
That's about as close as you're gonna get to Sprint OEM and the Sprint store would likely not even notice. I've been using this ROM for roughly 2 weeks and its been very stable.