Accented Characters for Cyrillic alphabet

Most of ex-soviet and slavic countries still use various accented characters build on Cyrillic alphabet. It would be great to have them when pressing and holding corresponding letter. E.g. press and hold "к" to have option to insert "қ", etc. If you need help, I can give you a list of accented characters for free. Nations, such as Kazakhstan, Tajikistan, Uzbekistan, Belarus etc. still use Cyrillic based alphabet along with Russian alphabet. Please consider seriously.