The question, already phrased in the title, looks like a classical problem from Banach space theory from the 1970s. Hence, my question is more of a reference request in its nature.
Can every separable Banach space with the metric approximation property be isometrically embedded as a 1-complemented subspace of a space with a monotone basis?
Perhaps this could be already achieved in some renorming of Pełczyński's universal space.