The biggest problem is getting everyone aligned, designing a plan with minimal rework, and being able to hire incredible talent that is going to cost far more than most companies are willing to accept.
For most companies they'll try with their existing talent and it'll be +5 years and an absolute failure.
And the very sizable opportunity cost of the engineering time spent on that project and not in anything more pressing. If your platform team has nothing better to do then I guess that's 1.5 years well spent, but if they have nothing better to do I have some questions about your company's engineering decisions.
The biggest problem is getting everyone aligned, designing a plan with minimal rework, and being able to hire incredible talent that is going to cost far more than most companies are willing to accept.
For most companies they'll try with their existing talent and it'll be +5 years and an absolute failure.