I've been slowly entering this hobby over the last 2-3 years. I probably took a different path to a lot of people. My profession is computing, my earlier passion is woodworking, and I stumbled across CNC and realised it gave me the best of both worlds. I bought a couple of different CNC routers over the years, and spent my time mostly building toys for my kids.
As I used the internet to research and learn, I had to fight my growing feelings of inadequacy. I didn't have a Tormach. I couldn't afford a Stinger. A Bridgeport wouldn't fit in my shed. How could I *possibly* do good work? I call this the "Binford Syndrome", after Tim The Toolman Taylor of 90s television fame, whose catch-phrase was "More POWERRRRRRRRRRR" ... a pre-cursor to the greed evident in the saying "He who dies with the most toys, wins."
How this ties back to the topic is that I think it creates an unrealistic picture in most peoples' minds of what is needed - in equipment and dollars - to take up this hobby. If someone thinks they need 100 m2 of floor space filled with tens of thousands of dollars in heavy machinery, they're not going to rush into hobby machining.
One way to overcome this barrier to entry would be to change the perception of what's needed to build model engines. As I read old magazine articles, for example, I often see amazing work created by hand tools. That might not be attractive to today's instant gratification society, but the lesson from those articles is that they demonstrate not just the engine, but the tools that were used to build it. Perhaps posters working on projects could more often share comments on the tools and techniques they use, rather than just the outcome. For example, I'd love to see more real-world uses of Taig and Sherline class machines, as these are far more realistic entry points for new hobbyists.
In line with the comments of an earlier poster, I'd also like to see more plans - even sketches - that were sized for these machines.
The second problem I face is the availability and cost of materials. As brass and aluminium become harder for the novice to find, probably in line with the death of manufacture in many cities, perhaps it is time to shift a body of work to modern materials such as resin, perspex, etc. It would be much easier to learn in this cheaper, more available material, even though I would still lust in my heart after the shine of brass and similar metals.
An experienced machinist could probably do this as a "no-brainer". A novice, though, needs recipes to follow. Simple plans that use widely available materials would go a long way to helping.
Finally, and perhaps a little more controversially, metric. In the vast majority of countries in the world materials are metric. Fasteners are metric. Tools are metric. A novice faced with plans in 1/8ths, 1/64ths, etc., and threads that no longer exist in his universe, gets treated like a fool by most materials and component suppliers. He asks for unrealistic product sizes, and items that no longer exist. A bit more work by the hobby in building a body of knowledge in contemporary measurement standards would go a long way to lowering the barrier to entry.
Just the thoughts of a novice, but perhaps relevant to more than just me