[CA] Upgrading and connecting Raymarine instruments to Garmin 7610 MFD

[Nokay]

(Great forum!)

I got a used sail boat that has the following configuration:

- Garmin 7610 MFD
- Garmin 18 HD Radar

The above are not connected to the Raymarine components, which are:

- ST60+ depth/speed tridata and wind
- SG3 autopilot computer
- ST6002 pilot controller

I'd like to do the following:

- Connect instruments to the Garmin MFD.
- Establish STNG bus to add NMEA 2K components in the future.
- Upgrade Tridata and Wind with new i70s displays.
- Avoid costly upgrade of radar, Garmin MFD or the S3G ... for now.
- Future: Upgrade pilot controller with new p70s controller.
- Future: Add AIS and GPS enabled VHF to STNG bus.

My questions are mostly around how to properly connect the pilot and Garmin MFD into the system in the near future (with ST6002 ST1 controller) and slightly more distant future (with p70s STNG controller).

It seems my options are:

1) Attach S3G to STNG using Raymarine ST1 to STNG converter and initially connect ST6002 to S3G via ST1 cable and in future simply add p70s to STNG bus.
2) Based on a separate post I read, maybe establish secondary STNG bus for p70s and S3G and somehow connect to primary STNG bus via STNG to ST1 converter or perhaps via NMEA 0183 to NMEA 2K converter. (If so, why?)
3) Connect MFD via NMEA 0183 to S3G (If so, why? Can I connect MFD via 2K bus in that case?)

Will under any option, pilot information become available on the Garmin MFD? Will the Garmin be able to control the S3G (not sure if that is possible under any option ... it is not an important goal of mine)? I would like to get heading from the fluxgate compass for example though.

Any insight would be greatly appreciated!

(Please see attached diagrams for my rough plan.)