I'd be curious to see if your change makes Mercer Ravannion's theories workable. If so, then I'd definitely say it would impact the wider universe. By your own admission:
7.5% extra mass to throw at weapons and armor is not trivial when you weigh 20 tons.
I had to look up Ravannion. It's an interesting read.
I'd argue his ideas were workable, he just picked the wrong horse to run. The canon vanilla Stinger & Wasp manage to be simultaneously too slow for its size, too poorly armored for its speed, and too toothless for the risk it poses to the pilot. Something like the Locust 1E beats them in each area while being cheaper, and would be much more workable as a swarm 'Mech, and it would actually be cheaper (C-Bill wise, not BV) to field. The Mongoose (MON-67) would essentially be like a Locust on steroids, though no longer cheaper than Stingers & Wasps. And if you don't require the emphasis on "cheap", there's always the Jenner. Any of these, though they might still not have
won the engagements, would have fared better.
It's an interesting idea though, if the Wasps & Stingers had ULJJs during Mercer's battles, would that have shift the tide in Mercer's battles? It's possible. Of course, using the extra weight for speed and another jump jet increases the cost by around 100k C-Bills, which is not a small amount. Since Mercer Ravannion was so cost conscious, he might have then turned to Fleas (FLE-14) as his go-to swarm mech.
Is there a scenario pack for Mercer's swarm scenarios? That change might be worth testing out on the field.