1)Landscape instruments should be improved, like more grids or subdivide landscape in some areas or whole landscape. Grid is especially matters, because when I turn on Pathtracer, i can see sharp sides of landscape model and its just looks ugly. Landscape tool must support more texture variences, and NOT ONLY FROM LIBRAR. Overall parallax maps improvement.
2)Water physics or any liquid substances
3)Pathtracer, too dark shadows even with the highest ambient points. May be there can be an option to manipulate with the shadows' tint or make them more enlightened ? Water material - transparency improvement. Weather ParticleFX support, like rain drops and snowflakes. Decals support.
4)Subdivide(subdivision)
5)Roundcorner (for sharp forms like box, making him like a chamfer box)
6)Proxy system as in Corona Renderer(allows user to choose between high poly model or regular model from basic library. Examples: vegetation, especially trees). Even, TM is presenting himself as a fast renderer, but you should know that there are some 3D professional artists, they want high quality images also.
7)More material maps like bump, AO, specular(not reflection), etc
8)Artificial Lighting system. Existing lighting instrument like Neon light, that have some invisible model inside, but visible in the reflection. These kinda bugs must be improved. Even with the IES light support(custom light shape textures), we want some really unusual types of lights, not just only box, spot or omni.
9)May be TM can switch to Unreal Engine 5 with their LUMEN and nanite system? Especially Nanite system. It can help us to make really BIG SCENES to present to customer.
If all these points will be done, Twinmotion can become a monopolist or at least major standard in the Archviz community, or even in other sectors of 3D art like Blender