Rollator or wheelchair suitability would also be covered by sac_scale and there would be no need for an additional tag for walking or hiking trails.
The main thing is that, like Hungerburg, I have difficulties with the definition given to distinguish between T0 and T1 in practice. What is the tolerable gradient, since hardly any trail is completely 0% flat?
What were the background ideas of the author of the strolling proposal?