I dont mind the stock feel at all but I also love to tinker. All I can really say is that shifter feel and shift knob weight preference is a little subjective. I feel like a heavier knob is my preference at the moment. I'm using the GR shift knob currently but I did have a lightweight wood knob installed for 4-5 months.
I did swap out the stock shifter springs for MTEC springs and I swapped out the shifter bushing for Faction Fab's bushing. NOTE the faction fab bushing is not a direct fit on the GR86, I had to 3d print spacers to make it work. I'm waiting on them to revise the design. They say it was tested on a BRZ so its possible they are different and could fit BRZ's possibly.
I feel like both of those items tightened up the shifter a tiny bit but maybe not a huge amount. Unfortunately when I installed these parts I ended up doing the shifter springs one side at a time due to needing to pick up a new socket, anyway I wasn't able to feel a before an after just a gradual one part at a time. This could be all placebo but I think I've had much less failed shifts and grinds from my own stupidity usuasally

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I know the new springs were stiffer than stock and the stock bushing was mostly air allowing for tons of movement compared to the solid polyurethane bushing.