No. Not yet anyway and it's unlikely to happen in the near future. It's either update and access eShop and related things or use the Gateway. The ONLY other option is to update to 6.2.0, use the eShop/data transfer one final time and wait for Gateway to update, but if you want to actually use the GW I recommend NOT doing that as it's a gamble.
Yeah that would probably work but that is no small project as you are going to have to crack the case and have some circuit board skills to put together the device to do the nand backup and restore. Sadly for now if you want the best of both worlds you really need 2 devices....one for OFW and one for Gateway. This is nothing new as generally you are running some type of risk with any exploited system using it online and it is generally not recommened.