Hoping to use mice ages 1d - 10 weeks and therefore hoping for a protocol that will work with all these ages. Aka perfusion is likely not an option at day1.
Collagenase digestion step is esential to liberate cells from stroma. So, before sacrifying animal inject some heparin i.p., remove liver in PBS with heparin, cut it in small pieces and treat with collagenase as usual.
Accutase, libertase and dnase I also could be used.
Depending of your aim you can try to homogenate liver without enzyme treatment, but it's bad way IMHO
D.R. Petrenyov's ideas should be explored. Each liver cell of interest for flow needs to be identified and "compartmentalized" prior to analysis. Interestingly, early EM studies (1960's) showed PBS infiltration of the vasculature caused endothelial cell death and improved hepatocyte preservation. My experience isolating liver cells for assessment of mitochondrial function relied on mechanical (and not enzymatic) using a Dounce homogenizer. You need to decide which of many hepatocytes you wish to explore. No single protocol will isolate all types.