Wait, what? World Trigger is clearly drawing on early Naruto & Bleach for inspiration, especially when it comes to establishing the supporting cast. Not to say that those are the only manga with large rosters, just that WT is definitely using similar means of expansion.
I also don't see that at all.
Bleach and Naruto established there support cast completely different from each other.
Bleach introduce it's characters in factions ichigo's school friends,gotei 13, arrancars,vizards,fullbringers with one member of group pretty much being a representive before the rest are introduced.
Early Naruto pretty much focused on team 7 & the rivalry within the team (naurto not wanting to lose to sasuke, sakura not wanting to lose to naruto & wanting to impress sasuke) then later it introduce more character as rivals for team 7 for the title of hokage and saskue love(ino & sakura).
World trigger way doing it is, it gives you an extended preview of it's support cast but flesh them out in the later arc,characters introduced in the in-fighting between A-rank agents got fleshed out in next arc (invasion arc), the characters introduced in the invasion arc got fleshed out in B-rank wars.
It current B-rank wars arc has more incommon with Hajim no ippo New challeger pre-fight character story except they get more screen time since they stick around a lot more after the fight, get a more extended preview and have far more of high chance beating team Osamu(main leads) then ippo and if they win or lose it's done in the graceful way both sides are shown in respectful light(no Nani? baka-ahna clowning).