Yes, you can!
I'm on an o3dsXL 10.3, but i franken-updated the eshop Nvar and the 10.5 friends system module so I can play games online too using 3dsNUS and packing the newer id and version of the 2 titles, the nvar for 10.5 and friends module for 10.5 into 2 cia files and installed them with NASA 1.2.
Keep in mind, this will give you a mismatched firmware of 10.3.0-30 but you'll be able to use badge arcade (if launched through grid launcher) and log into the eshop by running the eshop launcher (the one without the black I over it) in homebrew/grid launcher.
It'll still tell you that you need to update to use the eshop if you try launching it from the main system menu because your system menu isn't updated, just the nvar and the friends module.