Even without the SD card/flash this would be a useful feature, with the free memory I am typically seeing (at least 10Kb) you should be able to store data for around 40 minutes without even trying (10 data points, 4 bytes each = 40 bytes a sample, 10KB / 40B gives you storage for 256 samples, 2560 seconds or 42 mins).
I think from the conversations on Could emonESP also support CSV and post to a local emonHub? I think the larger issue was there is no way to bulk upload named values.
I say larger but it probably is not that bigger deal. A kind of hacky way of extending the current bulk upload may be to have some magic value for the time that indicates the values are names not values, eg ["names",0,"ct1","ct2","ct3","ct4","vrms","pulse","t0"]
I nicer solution would probably involve coming up with a new schema on a different endpoint.