I mean the raid suit made sense to me. It was a perfect Lure.
1. It gave Sanji access to power that he lamented not having when he was a kid (the powers of his siblings)
2. It gave him access to a dream he has wanted (Invisibility)
However, it made him make a choice. He could remain who he was, flaws and all. Or he could become this “indestructible warrior.”
The raid suit being destroyed and the speech Sanji says afterwards showed Sanji accepting himself. He accepts his flaws that came from the emotions his mother died to save, and he accepts his body as a modified human.
And by combining these Sanji was able to create a power all his own. His training gave him invisibility, and his emotions from his mother and exoskeleton from his father allowed himself deeper access to the fire ability that is unique to Sanji.
Basically, it’s similar to how Enma was a training tool, accept whereas Enma tested Zoros strength; the Raid Suit tested Sanjis character. If he accepted the easy path and taken the suit it would’ve destroyed him cause he’d lose his emotions until his fire died out making him nothing more than Stealth Black. An individual much weaker than Sanji.