Is there a normal character for every russian character to act as a replacement?
no. The only "normal" letters are
У, к, е, н, з, х, в, а, р, о, с, м, т
But all the others
Й, ц, г, ш, щ, ъ, ф, ы, п, л, д, ж, э, я, ч, и, ь, б, ю, ё
Wont be replaceable