I know that my post will not solve the problem, but hopefully it will shade some light on real cause and ask you to reconsider your expectations.
As DJI usually promotes their products as "idiot-proof" that proofing comes at the cost - in each FW iteration they pose more and more limitations in order to micromanage pilots attitude... Drones become popular and affordable, so many people fly close to the aircraft limit without having sufficient experience and without having idea how and why things can go wrong. So we all become "victims" of adjusting products to their insufficient experience, as each new FW and aircraft is built to protect them instead to give best tool to the pros... On the other hand, manufacturer pushes the limits of technology, cuts the costs as these are mass market products, and therefore manages the product to safeguard himself...
As far as I can tell, most battery cutoff, power throttling, speed limiting and similar performance degradations came simultaneously with the X5 cameras and Inspire1 v2 models. It must be that heavy load of X5 and X5R, as well as questionable airframe rigidity, motivated DJI to tame Inspire1 performance in favour of sufficient flight times and overall product reliably... Flying on the edge, thats what performance flying of X5 is really is, so DJI moved edge margin to be more conservative... Personally, I believe that on average, for majority of semi-pro-pilots, these performance degradations will not cause any regrets, while really experienced and skilful pro pilots will regrettably learn that Inspire1 is not real professional platform as it will not put you in full control of you airframe... If skilled and professional, you can regain some performance by flying in ATTI mode, or you can sell your Inspire1 and buy some real professional tools (as Freefly Alta, or some X8 airframe with DJI A2 controller)... I am Inspire 1, X5 and X3 owner, and personally I am ready to swallow the pill, and to give up some performance in favour of using exchangeable lenses of different focal lengths, while retaining relatively light and practical airframe... On the other hand, I know that there are some use cases where X3 camera on high speed airframe would make or brake a shot, but even X3 is not reliable solution as it easily shows vibration and jello at top speeds... Has anybody tried P4 at its top speed?