It is interesting that their calculation (based on the observed cosmological constant) gives a cutoff-scale that is not too far away from the Planck scale. They just used two scalar fields, a more realistic field content would be interesting.
What do you think of Christof Wetterichs way? He uses a quantum effective action to describe the Universe (as a transition between fixed points of RG flow) where the Planck mass is described as a scalar field ("variable gravity"). This model (where masses decrease in time and the Universe shrinks) incorporates very naturally dark energy. See e.g. https://arxiv.org/pdf/1705.00552.pdf (one in a series of many papers on this model). As far as I understand it, in his model inflation and DE are just two manifestations of the same. He also claims that his model is compatible with all current observations in cosmology, but I'm not really convinced yet.