The obvious S-Adenosyl methionine pathway may be interesting to explore on many levels ... it affects over 40 major methylation pathways including those of nucleic acids...

Perhaps a dead-end, but no one knows yet. Its use as a nutrient/nutrient supplement could affect this arena... SAM-e... etc.  An interesting angle/question.

could try supplements that are methyl donors; betaine, Vit B12, B6, choline, folic acid etc?

This is a shot in the dark, but if I wanted to increase global methylation, my first thought would be transient transfection of a de novo methyltransferase expression vector and concurrent folate treatment.