Hardware Swapping accounts between 2 systems

[DjoeN]

So i have a N3DS and N3DS XL (both on 10.3)

I've come to the conclusion i mostly play on the XL but my regular N3DS has all the bought games on it
while the XL has some bought games on it. i like to swap my accounts but keep old ironfall on both systems.
So the things i think to know are (correct me if i'm wrong)

- So i know i can't do that, swapping accounts in 1 go

Not an option, cause i lode IronFall on 1 system
- I know i can system transffer N3DS to N3DS XL (loosing all on N3DS XL), i can then call Nintendo and ask for a NNID transffer of the N3DS XL to the N3DS (loosing my old ironfall on that system)

Not an option (i don't think anyone is willing to borrow his N3DS to get wiped) , but most easy to use and to be sure to keep old IronFall
- Find a 3th N3DS (XL) i can borrrow for 14 days and wipe all, system transffer N3DS XL to borrowed N3DS, then wait 7 days, system transffer N3DS to N3DS XL, wait again 7 days, then transffer other N3DS (XL) to N3DS, voila, NNID's swapped.
- 7 days wait is needed when using a system transffer again on the same (N)3DS(XL)

So anyone have another solution to do it and keep old IronFall on both systems?
I know system transffer from N3DS to O3DS is not allowed, only from O3DS to N3DS or N3DS (XL) to N3DS (XL) (otherwise i wouldn't have a problem)