Strategies for successfully transitioning from MVP to “second system”?

From the lean startup perspective we have the principle of MVP, a really compelling and attractive idea for early stages SAAS-based businesses. On the other hand, for more mature stages of businesses, we have to be aware of the danger of "second-system effect" and have reasonable plans in place.

Now I come to my main question[1]: as a technical founder, how one can better prepare to avoid unnecessary and preventible (self-created) big technical problems while successfully transitioning from a (successful?) MVP to a good-enough (second but non-MVP) system, without endangering the whole SAAS business itself?

Thanks everyone for your thoughtful comments. Happy holidays and (in a few days) happy new year, 2022.

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[1] - We know a new business faces myriad of challenges that it needs to overcome; however, here, I focus on a single problem only for the sake of focused group discussion.