I kind of like the idea of Dousuru costuming Nobukatsu with an outfit that looks like the Meme Fodder Nobunaga painting, but I just reaaaaally don't like that Mitokomon sleeveless haori (chanchanko) that they used.
So if someone told me to redesign that costume to my own preference, these are my (very biased) offerings:
A) Very Strictly Historical: Just a standard daimon hitatare, but keeping the same colour scheme. Nothing special here.
B) Going Ham With Fancy: A Noh costume style kataginu and hakama, but cut to the wearer's size instead of big and bulky. The kataginu and hakama are embroidered with fancier designs, and a patterned kosode is worn underneath.
C) Ahistorical, but Relatively Simple: Based on a suou, a samurai formal wear, with the sleeves removed to be reminiscent of a kataginu. The sleeve slits are placed on the kosode, revealing the red innermost kimono/juban (may give the impression of slash wounds, can be used for dramatic flair/symbolism). This kind of design risks inviting protests from history-conscious viewers for being "weird", although maybe creative framing and camera cuts can distract the viewers from noticing.
D) Just Messing Around Now: Based on a suikan, a nobleman's attire that's also a Noh costume staple. Tied in the kind of casual tarikubi manner, to also make it more reminiscent of kataginu. It's a combination of the B and C concepts (Noh costume + formal wear), basically. Least likely to be acceptable for a Taiga drama, is probably more suitable for a fantasy/anime type of story.
(Designed for the role of Nobukatsu, despite the colour scheme, not Nobunaga)
(I also don't really like the actor cast in the role in Dousuru TBH, and the way the character is written, but that's another story)