3DS XL Nintendo Network ID linking

So, I've completed operations as planned and everything seems working as expected. Suppose you want to use new NewName as a primary NNID instead of old OldName with a possible minimum impact.

1. Register a new NewName user on a console, and follow standard procedure of creating new Mii and NNID. You can use same email as for OldName user.
2. Under OldName user, launch eShop and unlink Nintendo Club if necessary.
3. Under NewName user, launch eShop and link Nintendo Club if necessary.
4. Under NewName user, in user switch menu select Make Default.

That's it! You can still access all purchases made under OldName. Of course you lose all information associated with old account, most notably including save games (however some games have shared save files which are user-independent), friends and all Miiverse data. But as long as you keep old user you can always switch back to access it.

The short answer is 'NO'

All games you digitally purchase from the Nintendo eShop are tied to the Nintendo ID used for purchase. As soon as you change the Nintendo ID in your 3DS/3DS-XL, the old games become inaccessible. The only way you can regain access to them through your Nintendo ID would be to purchase them from eShop using your Nintendo account.