Early on the ball is quite slow. After ~15 minutes the ball goes quite fast. Enough so that slow Tems like Tortenite has to be practically perfect in making it to the first circle.
Speed changes are completely up to RNG and may never be offered in a standard 20 minute run. It's almost impossible to finish the event if it happens to go over an obstacle like a small gap or bench, as slower tems need to go in a straight line to make it in time. Dash helps a little, but is expensive and has to be unlocked on each Tem individually; dash distance changes can also make the dash effectively useless from over shooting.
The real threat for floor is lava is having to stand still to bounce the ball. The ball ramping up in speed only serves as punishment for playing a slow Tem, like Pigepic, Tortenite, or starting form runs.
So the suggestion: The ball is always a fixed speed. Something a little faster then round start, but not the crazy speed it hits late in a run that requires perfection.
The difficulty comes from being forced to stand still for extended periods of time and actually seeing where the ball is going on a busy screen. The timer could be increased even more as the run goes on to make up for the ball being slightly slower by the end.