-μι verbs have disappeared from Modern Greek; the conjugation of the verb ειμαι is formed by analogy with the middle voice
The imperfect forms agapousa is an early modern innovation from the third person plural ηγάπων reinterpreted as -οσαν under the influence of the sigmatic aorist φίλησαν; εφιλούν became εφιλούσαν and spread from contract verbs like φιλέω to other contract verbs.
All contracts blended together except -o- contracts which become -ωνω as in δηλώνω.
Modern Greek doesn’t care about the type of contraction, just that they were contracted.
The Modern Greek imperfect αγάπαγε in Ancient Greek was ηγαπα (long alpha contracted from a and epsilon became aje, reinterpreted as age if followed by a instead of e).