The distance from 'central Barrie' ('five points') to the Allendale GO station is a whopping 2.2km.
Having lived in North Simcoe for over 20 years, and having worked in Orillia, I'm not convinced there would be sufficient demand for commuter rail to Orillia. I wouldn't call weekday traffic on Hwy 11 between Barrie and Orillia anything close to being "extremely overcrowded". The only data I could find was from 2006 (Intergovernmental Action Plan- Simcoe County, 2006), but it found that over 64% of Orillia residents work in Orillia, with 30% working elsewhere in Simcoe County. Only 3.8% reported commuting to the GTA for employment. No doubt that has changed in the intervening years, but I doubt that significantly.
I heard my ears ringing......apparently someone called for 'The king of research' LOL
From: https://www.barrie.ca/City Hall/Pla...ter-Plan/Barrie TMP FINAL Report_20190612.pdf