I honestly don't see what the big deal is about swapping the lower parts over. It is not hard to do and I don't imagine you are regularly going to want to swap lowers. Am I missing something?
The only thing a 556 Lower (or clone) has going for it, is the ability to take AR-15 mags. For most Swiss Arms fans, I'm sure the original lower would be much preferred, if we were able to use standard capacity Swiss Arms mags in our rifles in the bush or at the range.
Since we're limited to 5 rounds for either non-restricted or restricted versions, the ability to use LAR-15 magazines with their 10 round capacity is appealing. As a hardcore Swiss Arms fan, this is the only reason this project would have any appeal for me.
I love the original Swiss Arms folding stock design and have zero interest in sticking on the latest AR-15 stock, which my American cousins seem so infatuated with doing, or any of a host of other AR accessories. If I wanted to kit out a rifle like that, I'd stick with my LMTs, Colts, Armalites, STAGs or ATRS ARs. For me, the original Swiss Arms ergonomics simply fit me perfectly, and I have no need or interest in screwing with that perfection (for me) or ruining the esthetics of the design. For those who want to tinker, all the more power to you!
I'm sure switching parts over from the OEM to the Neit 556 clone lower and vice versa, would get tiresome after about the second or third time. I know that personally, I would much prefer to keep my stock rifle, well stock and puchase a complete 556 lower that I could simply drop my upper onto in a minute or two.
I'm sure a better deal could be had for OEM small parts kits if you were ordering several hundred kits at one time as opposed to 1-2. If the cost of an assembled lower or stripped lower with OEM parts kit increased price of the Neit lower by several hundred bucks, I would pay it, simply for the convenience and for the ability to keep my Swiss Arms lowers intact and not screwed with.
Canadian Swiss Arms owners are a different breed than American 556 owners. The latter was built at a price point to compete with typical AR-15 on the American market ($1000.00+/-) and to allow American shooters to use/access their mountains of inexpensive AR-15 magazines. Swiss Arms rifles in Canada, as the closest thing you can get to the original 550 line in North America, were built with cost not being an issue. No corners were cut and Canadian buyers were willing to pay for this quality of workmanship. Thus you see the typical Swiss Arms rifle retailing for twice the price of the typical AR-15.
When you are spending that kind of coin, you don't want to go screwing around with swamping out lower internals, unless you're looking at doing a permanent switch and plan on tossing your Swiss Arms lower into your spare parts drawer. Somehow I don't see this option appealing to most Swiss Arms owners that I know.
That is why, a complete 556 cloned lower is of interest. It would allow me to use my AR mags when the mood strikes me without making near permanent alterations to my original Swiss Arms rifles. In all honesty, if the only option would be to switch the internals in order to use the Neit Arms lower, I probably wouldn't bother and would simply make do with my 5 round mags.