I would love to create, contribute to, learn from an RMH database. First, cudos to all who have spent countless hours doing video, writing book, and giving seminars. You've done heros work.
There are probably 10 years, or more, of experiments, designs, and methods, all pointing toward an efficient, easy design, yet no one person, or group of people, have created a go-to database of materials, mixes, criteria, limitations, dimensions and component parts (ie; heater cores, heat risers, ceramic "Lego"-type fire brick, or building blocks that work every time... and the 10,000 hours of knowledge available to wade through gets exhausting... I think to the point of many of us not feeling comfortable experimenting on our own.
There are numerous contributors, expert and novice alike, yet no great way to have it all in front of you, in well defined terms. For example, the occasional refractory cement expert contributes unbelievable knowledge, but those references are soooo hard to find again. Some have made headway in having refractory ceramic heat risers made in small quantitiy buys... yet I spend hours looking for that reference, or looking for the feedback, for example. I'd like to see us get to a point where several of us take on building generic parts that can be purchased (or made), and not have to re-invent the wheel hundreds of times over. These parts can be offered to the public for sale in a common forum, or even an ever growing catalog that is available on a forum, as well as providing info on "best mixes" of ceramic, perlite, cement, clay, cob, with a simple rating system for all the things that make, or break a project, ie; longevity, cracking, melting/heat resistance, thermal stability, availability, cost, ease of use.
How to get this idea evolved and rolling... I don't know, but if we get our heads together... who knows? There are many experts out there, and I'm not the one to compare the experts. I would start by listing the 5, or 10 best methods of efficient wood heating for instance (kacheloffen, masonry, RMH, batch, dragons, etc.), then try to simply rate them with efficiency, cost to make or buy, pros, cons, and continue breaking them down to component level parts, both homemade and purchased.
I could go on, but you can see how "off-the-shelf" parts or "comparisons of methods" would greatly ramp up the success of this great RMH idea that is a pillar of Off-Grid and Sustainable Living.