Bigger SD card, okay.
I assume with the Joy-con grip you mean the bridge part to make a dog face. Such a piece of plastic isn't expensive and should come with every SKU. The same goes for the My Nintendo coins.
Although the only difference between SKUs should be bundled games and/or additional controllers (as in, a Pro Controller), that way the lower priced standard SKU won't feel gimped. Better not repeat that Wii U nonsense.
I believe Wii U Deluxe had the little plastic cradle and the Digital Deluxe Promotion so its not unprecedented for Nintendo to offer things that cost nothing exclusively to one sku.
Pretty much anytime a company has offered a basic & premium sku, the basic ones sole purpose is to make the premium sku look like a better value so thats what i see happening here.
Personally i think a single $250 sku with 32gb, Splatoon and the other little extras would be better.
When the herd loses its way, the shepard must kill the bull that leads them astray.