I quite like this, I saw it last night and I'll be watching it!
I have swapped out many Tsuba for balance reasons in the past.
Bo-hi (or not), nagasa, nakago length, 'distal tapers' mixed with the actual applications of the final assembly (Iaido, Tameshigiri) a Tsuba at 155g is not a bad or weird thing.
I of course, can only relate to modern times, but I can imagine reasons for it in the past also.
To my very inexperienced eye, it almost seems the thick mimi was for the soul purpose of the nunome.