Your challenge is to find a way to make Great Moravia survive to the modern day. POD is in the 9th century, with Svatopluk I having only one son. If you cannot work with that, you may suggest another POD.
Modern day borders of Moravia must include at minimum OTL Moravia and Slovakia, but Czechoslovakia borders are preferred. If you can manage to also include Lusatia and/or Silesia, you will receive cake.
The country can fall under the influence of/be annexed by another country (as long as it regains independence by the early 20th century), but it must not be partitioned, and it must maintain a unified Moravian identity and language.