Currently in Survey123, accessibility options allow you make text and icon bold, have a plain background and haptic feedback as well as in another group, increasing the font size.
However, you can`t make the navigation icons (save tick/back cross) larger. Depending on the mobile device you may be able to increase display size however feedback from users is that this is annoying if moving between one app that is designed with strong accessibility for all users in mind so can be displayed at a standard resolution and Survey123 isn`t.
So, just an idea after speaking to staff about barriers to adopting digital ways of working, it would be great if the accessibility settings in Survey123 offered greater accessibility options to remove the barrier that some folks have of finding it hard to press exactly what you need to. And that's before you add the working outdoors and Scottish weather.