I think another solution would be to hold dedicated competitions for groups of events. More specifically there is an annual world FMC competition dedicated to specifically FMC. If this were to expanded to say a non-nxn puzzle comp or an only BLD comp we would be able to host a much larger variety of events within that category ( e.g. Curvy copter, Redi cube, Master Pyra for non-nxn and Mega BLD, team BLD, Squan BLD, etc. for BLD only comp ). This would completely take away the pressure to include every event at Worlds while maintaining serious competition in these events. This could work with the tiered system and you may be able to vary the structure of World ( i.e. including a list of classic events, the more/most popular events, and niche events on some sort of rotational schema ).Have you ever tried BLD events? 5BLD may have similar piece types to 4BLD, but if that's your only reasoning, why not remove 5x5x5 while we're at it? The memory skills needed for 5BLD are different than 4BLD at a high level - much of 4BLD can be done with mostly short-term memory, whereas 5BLD pushes into long-term memory like MBLD, although requires 100% accuracy and emphasizes speed over quantity.
Popularity of an event should always be put into context of the barrier to entry. Sure, lots of people are into 2x2x2/pyra/skewb, but it takes almost no effort to begin solving these puzzles. Difficulty/depth are valid qualities of an event, and if we solely used popularity to gauge new events, we'd just have shallow events like these.
Additionally, there should be no reason to remove events without reasons that go beyond redundancy and other subjective reasons. Rather than contract events, I'd prefer to expand the event lists. The only reason people think that there's a limit for events is to be able to hold them all at major championships, but I'd imagine that many would be ecstatic to have more events at local competitions even if they weren't at major championships. Tiered systems that define what events must/may(/cannot?) be held at majors would eliminate any real need to talk about removing events, just to talk about what is necessary at a major championship.