Your mission, should you choose to accept it: Replace the eponyms on all Phylloscopus warblers with accurate descriptive names that capture their differences. Go.
Western Bonelli's warbler,
Eastern Bonelli's warbler,
Hume's leaf warbler
Brooks's leaf warbler,
Pallas's leaf warbler,
Tytler's leaf warbler,
Radde's warbler,
Tickell's leaf warbler,
Ijima's leaf warbler,
Laura's woodland warbler,
Whistler's warbler,
Bianchi's warbler,
Alström's warbler,
Martens's warbler,
Blyth's leaf warbler,
Claudia's leaf warbler,
Hartert's leaf warbler,
Kloss's leaf warbler,
Davison's leaf warbler
There are many, many other Phylloscopus besides these, which look similar, so be sure your new names don't create confusion relative to those.
I don't think it's too difficult to come up with alternative names. Especially if you accept that the name doesn't need to exclude all other species (which is true for many accepted names in the genus: Greenish, Green, Two-barred, Yellow-browed, Wood, Willow, Chinese, Japanese, etc. - no-one is pushing to change these).
So here's some suggestions from a few minutes of brainstorming. I'm not familiar with several species on the list, so I'm sure people who know them could come up with better suggestions.
Western Bonelli's warbler: Green-winged Leaf Warbler
Eastern Bonelli's warbler: Balkan Leaf Warbler
Hume's leaf warbler: Wheezing Leaf Warbler
Brooks's leaf warbler: Acacia Leaf Warbler
Pallas's leaf warbler: Coronet Leaf Warbler
Tytler's leaf warbler: Kashmir Leaf Warbler
Radde's warbler: Short-billed Leaf Warbler
Tickell's leaf warbler: Tibetan Leaf Warbler
Ijima's leaf warbler: Izu Leaf Warbler
Laura's woodland warbler: Green-headed Woodland-warbler
Whistler's warbler: Himalayan Eyering-warbler
Bianchi's warbler: Upland Eyering-warbler
Alström's warbler: Plain-tailed Eyering-warbler
Martens's warbler: Chipping Eyering-warbler
Blyth's leaf warbler: Nuthatch Leaf Warbler
Claudia's leaf warbler: Qinling Leaf Warbler
Hartert's leaf warbler: Guangdong Leaf Warbler
Kloss's leaf warbler: Flicking Leaf Warbler
Davison's leaf warbler: Yellow-faced Leaf Warbler
Honestly I'm not really sold on all of this list. In particular I don't really like the name 'Eyering-warbler' but I do think this group of former
Seicercus would benefit from a name uniting them, and this was the best I came up with 😂