After thinking this through for some days and making a list of the pros and cons of different bikes for a primary and secondary bike, I've decided against ordering the Espin Nero. It would be fun, I'm sure, but it's not really the fit I'm anticipating long term as part of my two-bike set, plus I would actually rather get my preferred primary bike first and concern myself with a secondary later down the road, hopefully before next summer. After some experience on my chosen primary bike, it might influence what I then decide to get for a secondary bike, or perhaps my primary will become my secondary due to another primary preference.
So, at this point, if I decide to go ahead and order a primary bike soon for delivery in Sept., I've narrowed it down to either the
Ride1up 700 or LMT'D. Then before next summer, a Ride1Up Core-5 might make a nice secondary to the LMT'D. They use compatible batteries, so I could take along the battery from the other to extend range. But if I choose the 700, that's not an option. Either way, there's a lot more to consider. And if I hold off on buying a 700 or LMT'D now, I might end up choosing a different path before next summer, such as if an interesting new option pops up.