Hi,
First of all, you are right that MORe supports the ingestion of a dataset through an OAI endpoint. However, the used schemas in MORe are: EDM, ESE, OAI_DC, CARARE and OMEKA-XML. If another schema (e.g mods or mets) is used, then MINT should be used so as to transform the dataset to one of the above schemas.
This means that if you have a dataset in omeka-xml or oai_dc, you could immediately use MORe to harvest it.
I hope that it helps you.
All the best, Dimitra - Nefeli.