I wouldn't make a big effort since Wikidata phase 2 is ante portas, and it will provide coordinates. Not worth to deal with the task for a few months.
But if you are interested, you may want to take part in ongoing discussion about coordinates on Wikidata-l.
Is there someone who has or is wiling to share/make bot that will place coordinates template (in decimal format rather than DMS) at top or bottom of articles that have have not such template?
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