Frame breakage is a risk with low entry bikes like the Biria. If they make the frames strong enough to resist breakage the bike will probably weigh close to 50 lbs.
If I get to the point where I can't swing a leg over the saddle, I'll consider a dropper seat post. They're common on some new mountain bikes and might be adaptable to others.
I resumed cycling in 2015, after needing a cane to walk for about 14 years after a 2001 car wreck busted up my neck, back, hips, everything. Even though my fitness improved to the point that I could ride a conventional road bike by 2017, I still had a lot of stiffness and limited mobility in my lower back and hips. But I didn't do anything to improve it.
In 2018 I was hit by a car again, busting up my shoulder and neck. I didn't want to completely lose fitness so I started taking long walks, up to 5 miles, a few times a week. For a few months my hips ached from long walks but full body scans showed no skeletal or joint problems below the lower back. Just muscle pain, so I persisted until the hip pain stopped. I continued walking more even after resuming cycling in late 2018.
By late 2020 I added jogging to my routine, along with more body-weight exercises to improve flexibility and strength, including balancing on one leg while doing range of motion with the other. And on my usual 5-7 mile jogging route, I'll stop at the 2.5 mile mark at the crest of a hill to do a few minutes of leg, hip and back exercises before resuming jogging. It's helped and I have fewer problems kicking a leg over the bike.
Unfortunately my neck vertebrae are worsening so my days are numbered on a conventional bike. I've ridden very little since September due to neck pain, and no exercising will fix that problem. It's bulged discs, stenosis and other problems. I might eventually need to consider a recumbent. But not yet.