Here is a simple response. If you split Intel the design part will not be competitive with AMD, Nvidia, Amazon, Google, etc... Intel Design will be a cow out to pasture. AMD and Nvidia have close relationships with TSMC that Intel does not have. Pat Gelsinger made that happen. Can Lip-BU change that? Maybe but you will not see the changes for years to come. Meanwhile Intel design becomes less relevant.
Apple defined what a close foundry relationship should be 15 years ago with TSMC. TSMC has since expanded that to include other exclusive to TSMC customers like AMD and Nvidia. These companies have first line input into the process and PDK development plus packaging. We now call this "
Process-Design Co-Optimization". That is a big advantage!
Intel will do the same for 14A, Intel Design will be included in that inner circle of course but there must be others and that is what Lip-Bu is doing. He has the relationships to make this happen, absolutely.
Samsung is now doing the same with Tesla, Process-Design Co-Optimization. Elon Musk probably has a different name for it... Walking the fab floor?
Bottom line: The IDM model is evolving to better compete with TSMC. How long will it take? I do not know. Maybe 5-10 years but either it will happen or we will only have TSMC which is a very big risk all things considered.