But my point is that whether it's a good benefit or a bad cost is purely your perspective. If you change your perspective it's all good benefit or it's all bad cost.
Changing 5es terrible encumbrance to give s bonus when below the mark instead of s penalty after crossing it would do nothing to change that because the root cause in why people ignore it is the terrible design.
You miss the point. What was important is that there were two steps that mattered in different ways. The first one was tracked until you passed it and for all but the weakest characters the second one didn't really come up until "yea I'm sure all this puts me over". People didn't really track the second because it was a gentleman's agreement that kicked in when the GM said "your carrying a lot of stuff if you take all that". The first one was tracked for your standard kitbecause you got the benefits of faster movement and iirc better skill checks with some skills as long as you kept within the budget you worked out long ago & just keep tweaking.
"But I want to cheat" is not a good justification for ignoring encumbrance. "It's terribly designed almost explicitly to encourage players to forget about tracking a value that will almost never matter and accomplishes almost nothing even if they cross the line" is a very different thing.