You could have new large provinces. With it you can defuse political rivalries or keep them divided or promote them.
My take:
For Nicaragua
*East Nicaragua or Pacific. - OTL depts
North Caribbean Coast Autonomous Region and
South Caribbean Coast Autonomous Region
*Leon (around the city of Leon) - OTL depts
León Department,
Estelí,
Chinandega,
Madriz,
Nueva Segovia,
*Managua (the area of MAnagua including the shores of the Lake) - OTL depts
Río San Juan,
Rivas,
Masaya,
Managua,
Carazo
*Matagalpa - the rest of the depts not included above.
For El Salvador
*West-Central (Occidental) San Salvador (OTL depts from La Paz, Cuscatlán, Libertad and all the depts. to the west)
*East. Capital San Miguel. (OTL depts from San Vicente to La Union)
*Ïnterior - OTL depts of Chalatenango, Cabañas and Morazan and the northern tip of San Miguel
For Honduras:
*Caribe: OTL depts Colon, Olancho and Gracias de Dios
*Montañas (Mountains) Capital Tegucigalpa: OTL depts of El Paraiso, Choluteca, Valle, Francisco Morazan, La Paz, Comayagua
*Occidente (West) Capital San Pedro Sula: OTL depts Atlantida, Cortes, Santa Barbara, and the rest not included.