OSI and route issues Northern/Mildmay/Suffragette line

I have a Railcard on my Oyster card. Coming from a Zone 3 station on the Edgware branch of the Northern line, I sometimes travel to the high street near Harringay Green Lanes (HRY). There are quite a few options for this, with the following off-peak fares:

1) Change onto the Piccadilly line at Kings Cross and walk or take the bus from Manor House (£2.15 walking, £3.90 with bus)

2) Take the 113 bus to Finchley Road & Frognal and then the Overground to HRY (£3.25)

3) Take the Northern line to Belize Park (BZP), walk to Hampstead Heath (HDH) and then take the Overground to HRY. Because there’s no BZP-HDH OSI it gets charged as two separate journeys so this costs £3.00

4) Take the Northern line to Archway (ACY) changing at Camden Town (CTN), then walk to Upper Holloway (UHL) and take the Overground to HRY. ACY-UHL is an OSI so you get charged a through fare, but because there’s no fare route for this route, you pay the £2.15 default fare which for some reason assumes travel via Zone 1. This is the rail route that Citymapper suggests.

5) Take the Northern line to CTN, walk to Camden Road, then take the Overground via Gospel Oak (GPO) to HRY. This is the only route that triggers the avoiding Zone 1 fare of £1.50. But it’s quite a bit slower than option 4 above because you’re tied to the less frequent Overground for an extra leg, and you’re effectively doubling back on yourself for a few stations. Generally you end up on the Overground train 15 mins behind the one you’d catch if you did ACY-UHL.

This is a journey where none of the public transport options are particularly great in the first place, and the fares don’t particularly help either. To get the cheapest fare you have to go unnecessarily out of your way.

Firstly I am wondering why there is no OSI between BZP and HDH. Yes it’s not as short as ACY-UHL but as above, there are definitely journeys where it’s a logical interchange.

Secondly I am wondering why the default fare to HRY assumes travel via Zone 1. The only route I can think of that would involve this is if you change at Euston/Kings Cross and Blackhorse Road but this is so much slower that I can’t see many people doing it.

Finally I am wondering why there isn’t a fare set up that uses the ACY-UHL OSI given that it is the quickest and most logical rail route in my view, certainly more so than the only alternative fare which involves doubling back via GPO.

Is there any mechanism to get through to someone at TfL who can look into the above issues?