I would like to see them bring back the older designs
I have a DS50 and am amazed at how light it is and how easy it is to push and carry. I also have an Avalir and while it is heavier, I'm a 25-year-old in pretty good shape so it is no effort for me to push around with Tech Drive disabled. My HII Legend is effortless as well, although it is larger than my Dual Sanitronic in all dimensions.
I think that if they dusted off the plans of their 500-series/Sanitronic machines, added a fill tube (to enable the use of HEPA bags), modernized the shell, nozzle and handle fork a bit, they'd have a well performing, well built machine without the weight. I am of the belief that Tech Drive added to the bulk of the machine. If someone doesn't know how to use Tech Drive or doesn't know that it even exists, then yes, it's going to take a bit more effort to push. And, since Tech Drive Kirby machines have a few additional parts and a bit of a bigger footprint that the older ones didn't, it's going to weigh a bit more.
I actually don't want them to go to a different method to attach the hose and other tools to the power unit, since that is a hallmark Kirby design and it works well. The only way I would imagine Kirby pulling this off is to create some kind of capped inlet somewhere on the fancase or on the nozzle à la Royal. It wouldn't perform as well since I would assume some airflow would be drawn in from the floor nozzle. I know that having the hose sitting directly in front of the fan works really well as the airflow was just phenomenal when I used my Avalir to clean our vehicles. It performed better than my 6HP Shop Vac. Now, I will say that my wife and I have WeatherTech mats and leather seats in both of our vehicles but there's still some carpeting and little niches that still need vacuuming, and it does an awesome job. I know that the WeatherTech mat doesn't go all the way up the foot well and so dirt tends to gather there quite a bit. The small nozzle attachment on the hose of the Avalir effortlessly takes it all away.