I've recently become the proud new owner of a lovely late 90's steel road bike with some not so lovely "old school" gearing (53/39 chainrings and 11-25 8 speed cassette). As someone who both loves her knees and naturally keeps a relatively high cadence I am looking to change my bike have the option of lower gear inches. I know from my experience riding around on my touring bike that my ideal lowest gear inch option would be about 30 inches (using this to help calculate gear inches). I am including the different options I can think of with the relevant research I've already done below. I would love to hear what would be the easiest, cheapest way of achieving this and if there is some option I am overlooking.
Option 1. Get a cassette with larger cogs. The first issue I would worry about here is the rear derailleur which I believe is this one. The listed max cog size is 28t though I know Shimano recommendations tend to be a little conservative. Judging from the gear inch calculator I would probably need 32t or even 34t to get the desired minimum gear inches. If I needed to replace the rear derailleur would I be able to do that and still use the 8-speed Shimano brifters that are currently on the bike?
Option 2. Get smaller chainrings. The issue here is that the crankset on the bike has a 130 BCD so I think the 39t chainring is basically as small as is possible to fit on them (Sheldon's sheet suggests that the minimum for 130 BCD is 38t). So I'd need a new crankset and hope to find something that avoids other compatability issues (with e.g. the bottom bracket or the front brifters). Unfortunately, calculations suggest that even a 50/34 wouldn't quite give the desired minimum gear inches with the 11-25 cassette.
Option 3. Some combination of a larger cogs on the cassette and smaller chainrings. This option seems to require more work than either Option 1 or Option 2 and I'd guess it would be more expensive but I am not sure.
Option 4. Put a new groupset on and just make sure the new chainrings and cassette will provide the desired gearings. This one is definitely the most expensive and requires the most work but I am including it for completeness.
For reference, I plan on doing most/all the work at a local free "Open shop" run by a non-profit dedicated to teaching people how to take care of bikes but if anything is very technical/hard/requires special skills I may go to a LBS for that.