Sorry, but this is a ridiculous discussion.
Ridiculous for which reason?
1) Processors cannot have their firmware / microcode changed after some event before Intel packages them for sale, i.e. they have been finalized.
2) Intel does not want to do it because it would cost a great deal of money.
If #1 is true, then I completely understand, as it is a technical bar. But if #2 is true, I disagree, as Intel could tell the many lawyers drooling at the prospect of possibly the largest class action suit in technology that it is mitigating the problem. Remember that Meltdown affects almost all Intel processors, along with a few ARM ones, but no AMD processors, so Intel's argument that it affects all vendors is simply not true. The two varieties of Spectre do affect all vendors, however.
My proposed solution would not be perfect or fair, as Linus Torvalds stated that performance degradation will be 5% for many people, but applications that perform many system calls, e.g. database servers, will suffer much worse.
What you are probably misconstruing is the practice of binning which is the process of testing each die to figure out what speed it is able to run at.
Additionally you also need to understand the concept of Thermal Design Power (TDP). An i5-2405s likely has the same die as an i5-2400, but the TDP of both is very different.