Is it possible to deploy the fix today if possible and not early next week? The issue is that this basically means very limited capacity to edit Wikidata for those whose alphabet is different from Latin.
Turnaround solutions exist (omitting, replacing these characters with characters in different case or characters from other languages) but they are difficult to fix in longer term. For instance, if I want to type Wenckh von Wenckheim in Cyrillic, I cannot type "Венк фон Венкхейм" as х is banned. I can type "Венк фон Венкейм" (omitted, i.e. Wenckeim), "Венк фон ВенкХейм" (uppercase, i.e. WenckHeim) or "Венк фон Венкxейм" (latin x, i.e. Wenckxeim), but all these spellings are wrong. If we let people do it for three or four days instead of few hours, those turnarounds would be way more difficult to find and fix.