Datacratic has been doing what you ask for a while now (disclaimer, I work for them). We do ML, audience optimization, segmentation, multivariate and nonlinear

Datacratic has been doing what you ask for a while now (disclaimer, I work for them). We do ML, audience optimization, segmentation, multivariate and nonlinear models for small clients or for some of the largest shops in the industry. But the algorithms are indeed a small problem compared to building the on-demand infrastructure, managing the dataset, and all the rest of the challenges related to managing other people's data. Trust to handle data that doesn't belong to you is earned with great difficulty, unless it comes from shady sources.