But I was stupid enough not to even try.
I did try now and, yep, I got it working!
How I installed it:
** Remember: Your device must be capable of 720p video decoding and rooted, unless YouTube is not preinstalled as a system app!
• Removed /system/app/YouTube.apk
• If YouTube is still in the app drawer, go into YouTube app info and tap "Remove installed updates", then "Force stop".
• Install my APK!
If that doesn't work for you, try this alternative method:
• Remove YouTube.apk from /system/app (if there is any)
• Uninstall YouTube if it's still on the drawer
• Push my APK into /system/app (be careful with permissions / ownership)
Downloads
Android 2.2 or newer (Froyo/Gingerbread/Honeycomb/Ice Cream Sandwich/Jelly Bean)
v4.1.23 - WiFi HD | WiFi + 3G HD
v4.1.23 Inverted (Dark theme) - WiFi HD | WiFi + 3G
v4.1.23 WiFi + 3G HD with screen off (locked) playback: Classic / Inverted (Dark theme)
http://forum.xda-developers.com/showthread.php?t=1529715
