Hello,
as a professional creative, I put many hours into Affinity Photo since it came out. For now, using in around Photoshop. However, without I cannot open a PSD file that can read all variances of layers (e.g smart layer) it's really not applicable to a replacement. Most of my clients, art directors, designers and photographers work and send layered PSD files with smart layers.
I am a big fan and hope that you can add those little features soon. I know by reading a lot here that you are working on it and replicating all features is hard.
Cheers
David