I voted for speakers, because I think they are the worst part of the laptop currently. But I know not that many people care about them anyway.
Apart from that I think the software could use some improvements. I think there should be some ways to reduce power usage in idle even more and sometimes suspend->hibernate on low battery is not 100% reliable.
Regarding the screen, I do think it is great, but it would be a lot of fun to have a touch screen and variable refresh rate supported as well as have it use less power (possibly via PSR or the new thingy as well as VRR).
I think the battery swelling, that is currently fixed in software, should be fixed in hardware as well long term and more battery life is always nice, but it isn’t as critical to me.
The keyboard is great, but addressable RGB would be really great, especially for my clear keyboard! Ah, and QMK (or similar) of course! You already fixed the rattling from the speakers in newer revisions afaik, so I wouldn’t know what else to do there.
Cooling seems fine, but making the fan individually serviceable would be very appreciated, especially for cleaning. Fan could be quieter and tuned better, but I think most of that is software, maybe some additional heatpipes or layout improvements. Not a priority for me though.
I would also like more colour options for the chassis, but currently I am just painting it myself, which is fine for DIY, but a bit tedious and wasteful compared to doing it from the factory.
Random thought, but would a bezel with an included privacy screen be possible? I recently had to buy one for my company laptop, so having the option on the FW13 might be nice!