Hi,
This is a great site and I'm pleased that you are pushing wheelchair design forward. It needs it as most commercial chairs focus on the wrong things, rather than the fundemental.
I've been altering chairs ever since i first had to sit in one, some 40 years ago. I'm a tetraplegic with an enthusiasm for design, engineering and making things work better. I've altered cars, chairs, aeroplanes and boats. I count myself very fortunate to be able to pay for this work, as i cannot physically undertake the work myself. The biggest projects have been aircraft, in which I established a company, raised sponsorship and had to work closely with the CAA and airworthiness engineers. Wheelchairs are the main target of my activity, although i don't change motors or control systems. I've changed caster designs, wheels, moved lights, changed seats, redesign lifters, added leg bag emptiers, reupholstered, added different tie-down systems, solenoid locking pockets (stopping theft), and more. Much of my work has been making chairs easier to live with such as nerf wheels (so skirting boards & doorways don't get damaged) and other stuff. Other changes address the fundemental limitations of the chair, such as structural design and making footplates flexible so them don't break.
If anyone would like details of the leg bah emptier, I'm happy to share. This allows me independance throughout the day! I also use a lot of key retractors to attach phones, wallets as I tend to drop things. Once on the floor they stay there. There are lots available - i suggest one with a long strong cable.
All the best, Philip