AWD
And not just AWD on the base engine, available AWD across the lineup and engine options would be amazing. Honda offers AWD on every other vehicle in it's lineup besides the Civic and Accord. Honda has the platforms, Honda has the parts, Honda has the ability. Camry pairs AWD with their base engine, same with Nissan and the Altima and the Kia K5; Subaru pairs AWD with everything. If automakers want to stop pretending that the only thing consumers are interested in is SUVs, they need to start making their sedans competitive in relation to SUVs. I'm in the Midwest and (anecdotally) the main thing that draws consumers to SUVs is the availability of AWD.
I would gladly pay the $1,500 (the price Honda charges to add AWD to the rest of it's lineup) extra on top of my Accord Touring price. I don't care if Honda is trying to buffer Acura; an AWD 2.0T TLX needs to be speced over $48,000 to get the same features as the Accord Touring. I test drove a TLX and while I think it looks amazing, it didn't wow me enough to justify the significant price hike compared to the Accord. Likewise for any of the other premium/luxury sedan offerings from BMW/Audi/MB/Lexus/etc; the prices for their AWD variants with any of the features you actually want are almost $50,000 (or your stuck with a subcompact car).
Interior Color
The interior on the 10th Gen Accord is pretty good. It's reviewed well, and in my 40,000+ miles it's held up really well. But Honda needs to include a different interior color/color combination than just Black/Black. I think Honda offered a white interior on earlier year 10th gen Accords, but on their website and in almost every 2021 Accord i've seen, they only offer black interior. It just looks so bland. The German premium brands used to get flack back in the day for their black on black interiors being so drab. I think it would really help interior styling if they had some light(er) options.
LSD
IF no AWD option on higher output engine trims, at least offer or include a limited slip differential. I don't know how or why Honda included a LSD on the Civic SI, but no on the Accord Sport 2.0 or the Touring 2.0. If the price could be built into the lower Civic price, I don't see why it can't be built into the low selling higher engine trims. It would greatly help with power application. The current 2.0 Accords (and plenty of other FWD turbo cars) have way too much casual wheelspin.
New Rims
I don't care about the 19 in rim size, but for the love of god... PLEASE redesign the rims so the metal rim doesn't stick out further than the rubber tire. People complain about curb rash and the "hur-dur-durp" response is always some version of "learn how to drive." But seriously, go look at one of the 19 in rims head on and you can see the issue. Usually, the rim is more inset of the tire, allowing a slight buffer. I've driven plenty of big-rimmed cars before, including my partners BMW, and i've never had the issues with curbing as I have with this car.
Actual TPMS
An actual tire pressure monitoring system that can read each wheel individually and display current tire pressure. NOT the current wheel rotation sensing system that just tells you one of the tires is low.
Trunk Pass-through
Not sure why this was removed, my 8th gen Accord had it. But I miss the little cubby/door in the middle back seat where I could quickly toss things into my trunk.
Audio/Infotainment System
I'm hoping the Accord gets the Bose system in the 11th gen Civic. I'm no audiophile, so I don't need some groundbreaking audio system, but the "premium" system in my Touring is pretty meh.
More specifically, if they are going to continue to place the subwoofer in the rear deck, they NEED to better insulate or reinforce the back shelf. I didn't care that the premium sound system wasn't the best, but what was insanely annoying and embarrassing is the rear deck bass rattle. Despite taking the car to Honda more than once, showing them the known bulletin for the rear deck rattle, they never fixed it. So ... there's a sock bunched up between the rear window and the rear deck to help stop the rattle.
On the same topic/area, they need to have a better infotainment system. Mine has been buggy since day 1. Multiple trips to the dealer, multiple resets, and its still a buggy mess. I'll be fair and say it's probably a mix of the infotainment system and Android Auto. But I can't imagine that the infotainment system is helping Honda's reliability scores (that take into account infotainment complaints and can weigh them the same as mechanical complaints. not apples

ranges, but something to consider).