I'm not convinced. I really dislike the idea of having two products ? what if I want to use both 2-D and 3-D together? It also depends just how much 3-D capability would be incorporated ? if it's just simple displaying of a model and maybe some basic lighting, There's no reason to redo anything from scratch when it can be made as a plugin instead. Making two products would be far, far more work for Ashley for no reason.
I'm also not sure how it would be better. The only thing I can think of that there might be a potential issue with is panning around a 3-D world in the layout editor. I can imagine that could be worked around elegantly by having a 3-D camera that's separate from the normal 2-D one that the user can switch between.
I don't want a separate product either, but I'm convinced that adding 3D support onto construct2 would be a nightmare that would delay other (much more important) features.
Like you said, even something simple such as panning around in the editor would require coding a separate camera and rendering engine - if you have a product that has two modes, it's basically the same as having another product.
I get that you want to be able to use 3D stuff in normal projects, and I agree - I've wanted to do that many many times - here's an example:
On a space game I'm working on, which is practically all 2D, one of the features is being able to choose a site on a planet to land on. Creating a 3D sphere with animated textures spinning around (simulating a planet) was a huge pain. Also, mapping mouse coordinates onto planet surface coordinates had to be done by hand using math. This would have been relatively simple to implement if C2 supported even basic 3D capabilities.
Still, I think it would be better to have a mainly 3D product that is 2D capable than the other way around.
Even if Ashley didn't intend to incorporate 3-D from the start, that doesn't necessarily mean that it will be difficult to implement. It might be, but you seem to have decided that it will be difficult and wouldn't succeed without knowing the underlying architecture like Ashley does.
Yes, it does not necessarily follow that it will be hard to implement - but trust me, it will. Though only Ashley can confirm this.
That doesn't mean a 3-D engine would generate too much garbage as well. They're not the same thing.
I said that to illustrate how, even with a well planned feature, problems happen. A 3D engine isn't likely to generate a lot of garbage, due to such engines usually being extremely optimized, so yes I'll agree there.
Here is a better example: most (if not all) 3D engines are meant to be used as a foundation for the rest of your engine, unlike box2d which is designed as an add-on. This means that, even if Ashley wanted to add 3D, it would need to be made in-house.
Anyway, it's irrelevant because Ashley has said that there are no short-term plans to add 3-D, so even if it does get added eventually, it'll be quite a while until then. Unless some third-party plug-in developer makes it first.
I don't think the chances of something good coming out of third-party plugin developers are in our favor. Look at MMF2: all those years third-party devs have been attempting to add 3D via extensions, with limited success (and poor quality overall - their best results are stuff like mode7).
Maybe the shader guys have more luck.