As a user of an off grid solar system I would like to replace my lead batteries with your compressed air solution, even with efficiency of less than 70% it will work for my needs, because with larger capacity I will be able to collect a lot of energy during summer and use it during cloudy winter.
Also I think you should consider doing a MVP (minimal viable product) with less efficiency but fully functional (as I understood from your blog you're struggling now with improving efficiency) and test it in real life, I think there are a lot of off the grid users in US who would like to test it, because real usage is very different than testing it in lab. You'll be able to test a lot of hardware components and be prepared for larger adoption.
An MVP is a totally different think when you're talking about electromechanical equipment that needs to attach to the grid. You need to work so hard just to get something out of the door, you might as well make it good.
Luckily, the market is decently easy to figure out by discussions and logic.
Also I think you should consider doing a MVP (minimal viable product) with less efficiency but fully functional (as I understood from your blog you're struggling now with improving efficiency) and test it in real life, I think there are a lot of off the grid users in US who would like to test it, because real usage is very different than testing it in lab. You'll be able to test a lot of hardware components and be prepared for larger adoption.