Norbs, welcome to the forum
oh
Surely if this question is aimed at creating the ultimate bat – we have a problem, which is different players hit the ball out of different areas of the bat – so to create the ultimate bat – there is no solution, without making something individually designed for the player – and you haven’t even mentioned the variable of the pitch yet (slow and low, two paced, variable bounce, or hard and bouncy...). Further, bat speed is dependent on the batsman, in the same way swing speed is in golf – so it is difficult to have a massive impact on that with a cricket bat, I have tried using a heavier bat and lighter bat and timing is the most important thing. Try comparing Tiger Woods to Ian Woosnam.
However, surely we are better looking at the type of bowling that you are trying to hit – given that variations of pace are coming into the game more than ever, as well as the continued prevalence of the yorker, you need a bat which you can manipulate the low full toss for four, or the miss judged slower ball into a gap for 2, whilst still being able to smash the real rubbish out of the ground.
Not sure I have been any help here. On that basis you should use the biggest bat you can comfortable control, so for some it will be a 3lbs railway sleeper, whilst for others it will be a 2lbs 6oz wand.
The key then must become the length of the middle and the rebound qualities (how well the bat is pressed) as well as the natural timing of the player. If we all had the natural timing of VVS then cricket would be a much easier game...
I am going to stop now as I have no real idea what I am talking about.