Your manager looks at you, silently thinks it over for about 0.35 seconds and then solemnly states: that sounds like a plan, make up the Gantt chart and deliver it to me, I'll take it to the boss.
And so it is done. You have taken the first step to re-write (from scratch, obviously) that part of the system. Did you make the right decision? You say only time will tell?
I beg to disagree, and so does Uncle Bob. You just made the most stupid, crazy-ass, fully incompetent, narrow minded, ignorant, and hole-digging decision of your life and soon you will regret it. Hopefully for the rest of your life, so that you don't do it again!
Re-architecting (read re-developing from scratch) a part of your system is the single most waterfall-ish idea that could cross your head -- and it will make you fail...
I've been a developer that made that decision, and still regret it today.
I managed a project where I was the one accepting to re-implement that part of the system, and still regret it today.
And if that was not enough a colleague at work did the same decision and he is already in his 3rd re-implementation of a module that should take 2 weeks to implement (his words) and he has been at it for more than a year... (his boss is still saying "ok" after thinking about it for 0.35 seconds...)