Yes, I do think he's more of a scientist, which is aligned with what we know about him from the novel: Jin Yong consistently emphasized his theoretical expertise much more than his practitioner side (which got almost no mention), so I believe what Jin Yong had in mind was a great philosopher and experimental scientist, not in particular a strong practitioner -- which is not to say he's not a good practitioner, it's just not his strongest point.
But you haven't shown which characteristics that Zhang Sanfeng has demonstrated in the novel inform us that he's like an engineer.An engineer has to APPLY (the key word) his theoretical knowledge into practice. That means implementation is every bit as important as the theoretical design.
I don't go around proclaiming that Xiao Feng is like an engineer when most evidence in the novel indicate he's a technologist.
Lab practice which has not been translated into combat experience.Think of Z3F's 100+ years as his lab practice.
The novel implied that Zhang Sanfeng hasn't fought anyone in combat for 20+ years, so that's hardly 100 years of practical experience.His taijiquan is the ultimate product of his theoretical knowledge and 100 years of practical experience.
Sure; Huang Yaoshi, Yang Guo, and Zhou Botong come to mind. They didn't create as many martial arts as Zhang Sanfeng, and they can't quite compete with Xiao Feng as the God of Fighting, but they are well-rounded in both arenas.Seriously, can you think of any other fighter (besides Sweeper Monk, Dugu Qiubai or Bodhidharma) that is a master at both the theoretical and practical? It's either you're very good at the theoretical principles and poor at implementing it, or you're very poor in the theoretical principles but good at implementing it. It's very rare to master BOTH the theoretical and the practical.