No problem. I did it that way. Just sideload the zip in recovery without wiping the data.
No problems at all. Everything’s running fine.
Just two things if you update to 3.0 that way:
First
You have to clear cache and data in bluetooth app after first start in 3.0. Otherwise if will crash permanently.
Settings/apps/ - show system apps - bluetooth apps
Second
Enable developer settings
Enable “deactivate bluetooth a2dp hardware offload”
Reboot
Otherwise bluetooth audio is not clear