Drop anything having to do with analog video, including component video. This will allow space and budget for other enhancements, likely reduce noise levels, and eliminate an aggravating piece of outmoded technology.
Use AKM AK4493 DAC's, which are the latest generation and replace the current AK4490 in AKM's lineup.
Use 1% metal film surface mount resistors in key areas instead of metal oxide units. These don't cost much, and have lower distortion and noise.
Add support for 4 subwoofers instead of the current 2.
Replace the porthole display with a much bigger, rectangular display; or upgrade the porthole display to a high resolution OLED display, and provide an everchanging undersea view with a user selectable choice of fish and other interesting sea creatures.
Eliminate all jumpers on circuit boards by using 4-layer boards as needed. The goals is to reduce noise.
Connect the HDAM connector boards to the main circuit boards with connector circuit boards, not wires. The goal is to reduce noise and crosstalk.
Full support for HDMI 2.1.
Add another volume control chip. With other changes this will allow features such as maintaining the L&R XLR input signals at a high level, and balanced, through the unit, to improve signal to noise performance, instead of attenuating the signal and converting to single-ended. This will make the XLR input more of a premium input. Enhancements to the analog output circuitry for the L&R channels, that support the L&R channel DAC, would enhance the quality of stereo signals that originate in digital form. Such improvements in stereo performance might cause some people to use the AV8805 for really high quality stereo listening as opposed to this same set of people making significant added investments in pure stereo gear.
Increase opamp supply voltages to a minimum of plus or minus 12 V.
Upgrade the opamps to at least 5532's, which are cheap.
Move production of the product to Vietnam or another low cost country, if required to maintain, or preferably lower the current price and add the above features. The AV7704, for example, is very well made, and it is produced in Vietnam. From a normal seating position it is impossible to see the country of manufacture lettering on the back panel of the unit.