Probably not, prep time is a very vague term as it usually involves hundreds if not thousands of possible scenarios. I literally cannot think of any thing that prep would allow to beat someone like Asura.
Every character gets overrated, it's nothing new, then again Batman has feats like formulating a plan that spanned the dawn of time to the end of the time that stopped Darkseid from destroying all of reality...It'\s not that Batman couldn't beat Asura with several years, I just can't think of anything he can do to stop someone like that.
Like I can easily say that Batman can create a device that would drain Asura..but how would he make it??...these are better questions to ask..
Maybe Batman borrows the Warlogog? Or a phantom zone projector?
No idea how Batman could really prep against someone that could play marbles with planets..
__________________ What CDTM believes;
Never let anyone else define you. Don't be a jerk just to be a jerk, but if you are expressing your true inner feelings and beliefs, or at least trying to express that inner child, and everyone gets pissed off about it, never NEVER apologize for it. Let them think what they want, let them define you in their narrow little minds while they suppress every last piece of them just to keep a friend that never liked them for themselves in the first place.