I compiled a list of Indian Civs with their respective dynasties/kingdoms/empires in the medieval era. Of course I may still be missing a few names in the list, if you notice any, you can point me out. But it gives you an idea why Indian Subcontinent needs more than one civs in order to be represented properly in AoE2 timeperiod.
Assamese
https://en.wikipedia.org/wiki/Kamarupa
https://en.wikipedia.org/wiki/Khen_dynasty
https://en.wikipedia.org/wiki/Chutiya_Kingdom
https://en.wikipedia.org/wiki/Ahom_kingdom
https://en.wikipedia.org/wiki/Koch_dynasty
https://en.wikipedia.org/wiki/Bhuyan_chieftains
https://en.wikipedia.org/wiki/Kachari_kingdom
Bengali
https://en.wikipedia.org/wiki/Gauda_Kingdom
https://en.wikipedia.org/wiki/Mallabhum
https://en.wikipedia.org/wiki/Pala_Empire
https://en.wikipedia.org/wiki/Sena_dynasty
https://en.wikipedia.org/wiki/Karnat_Dynasty
https://en.wikipedia.org/wiki/Deva_dynasty
https://en.wikipedia.org/wiki/Oiniwar_Dynasty
https://en.wikipedia.org/wiki/Raj_Darbhanga
https://en.wikipedia.org/wiki/Chandra_dynasty
https://en.wikipedia.org/wiki/Bengal_Sultanate
Oriya
https://en.wikipedia.org/wiki/Sharabhapuriya_dynasty
https://en.wikipedia.org/wiki/Nala_dynasty
https://en.wikipedia.org/wiki/Panduvamshis_of_Dakshina_Kosala
https://en.wikipedia.org/wiki/Somavamshi_dynasty
https://en.wikipedia.org/wiki/Eastern_Ganga_dynasty
https://en.wikipedia.org/wiki/Gajapati_Kingdom
https://en.wikipedia.org/wiki/Parlakhemundi_Ganga_dynasty
https://en.wikipedia.org/wiki/Kingdom_of_Jeypore
https://en.wikipedia.org/wiki/Soroda_dynasty
Hindavi
https://en.wikipedia.org/wiki/Nagvanshi_dynasty
https://en.wikipedia.org/wiki/Maukhari_dynasty
https://en.wikipedia.org/wiki/Tomara_dynasty
https://en.wikipedia.org/wiki/Gahadavala
https://en.wikipedia.org/wiki/Chero_dynasty
https://en.wikipedia.org/wiki/Pushyabhuti_dynasty
https://en.wikipedia.org/wiki/Hindu_Shahi
https://en.wikipedia.org/wiki/Jaunpur_Sultanate
https://en.wikipedia.org/wiki/Delhi_Sultanate
Sindhi
https://en.wikipedia.org/wiki/Brahman_dynasty_of_Sindh
https://en.wikipedia.org/wiki/Chavda_dynasty
https://en.wikipedia.org/wiki/Rai_dynasty
https://en.wikipedia.org/wiki/Habbari_dynasty
https://en.wikipedia.org/wiki/Soomra_dynasty
https://en.wikipedia.org/wiki/Samma_dynasty
Gujarati
https://en.wikipedia.org/wiki/Kalachuri_dynasty
https://en.wikipedia.org/wiki/Maitraka_dynasty
https://en.wikipedia.org/wiki/Saindhava
https://en.wikipedia.org/wiki/Chudasama_dynasty
https://en.wikipedia.org/wiki/Vaghela_dynasty
https://en.wikipedia.org/wiki/Chaulukya_dynasty
https://en.wikipedia.org/wiki/Gujarat_Sultanate
Rajputana
https://en.wikipedia.org/wiki/Malavas
https://en.wikipedia.org/wiki/Aulikaras
https://en.wikipedia.org/wiki/Chahamanas_of_Shakambhari
https://en.wikipedia.org/wiki/Gurjara-Pratihara_dynasty
https://en.wikipedia.org/wiki/Paramara_dynasty
https://en.wikipedia.org/wiki/Yajvapala_dynasty
https://en.wikipedia.org/wiki/Malwa_Sultanate
https://en.wikipedia.org/wiki/Sisodia
Kashmiri
https://en.wikipedia.org/wiki/Karkota_Empire
https://en.wikipedia.org/wiki/Utpala_dynasty
https://en.wikipedia.org/wiki/Lohara_dynasty
https://en.wikipedia.org/wiki/Shah_Mir_dynasty
Nepali
https://en.wikipedia.org/wiki/Licchavi_(kingdom)
https://en.wikipedia.org/wiki/Limbuwan
https://en.wikipedia.org/wiki/Khasa_kingdom
https://en.wikipedia.org/wiki/Malla_(Kathmandu_Valley)
https://en.wikipedia.org/wiki/Kallala_dynasty
https://en.wikipedia.org/wiki/Gorkha_Kingdom
Tamil
https://en.wikipedia.org/wiki/Pandyan_dynasty
https://en.wikipedia.org/wiki/Chola_dynasty
https://en.wikipedia.org/wiki/Sambuvaraya
https://en.wikipedia.org/wiki/Vanni_Nadu
https://en.wikipedia.org/wiki/Jaffna_Kingdom
https://en.wikipedia.org/wiki/Madurai_Nayak_dynasty
https://en.wikipedia.org/wiki/Thanjavur_Nayak_kingdom
https://en.wikipedia.org/wiki/Kulasekhara_Dynasty_(Second_Cheras)
https://en.wikipedia.org/wiki/Madurai_Sultanate
https://en.wikipedia.org/wiki/Venad
https://en.wikipedia.org/wiki/Zamorin_of_Calicut
https://en.wikipedia.org/wiki/Kochi
Kannada
https://en.wikipedia.org/wiki/Kadamba_dynasty
https://en.wikipedia.org/wiki/Western_Ganga_dynasty
https://en.wikipedia.org/wiki/Chalukya_dynasty
https://en.wikipedia.org/wiki/Rashtrakuta_dynasty
https://en.wikipedia.org/wiki/Western_Chalukya_Empire
https://en.wikipedia.org/wiki/Hoysala_Empire
https://en.wikipedia.org/wiki/Vijayanagara_Empire
https://en.wikipedia.org/wiki/Badami_Chalukyas
https://en.wikipedia.org/wiki/Bahmani_Sultanate
https://en.wikipedia.org/wiki/Seuna_(Yadava)_dynasty
Telugu
https://en.wikipedia.org/wiki/Vishnukundina_dynasty
https://en.wikipedia.org/wiki/Eastern_Chalukyas
https://en.wikipedia.org/wiki/Kakatiya_dynasty
https://en.wikipedia.org/wiki/Reddy_dynasty
https://en.wikipedia.org/wiki/Musunuri_Nayakas
https://en.wikipedia.org/wiki/Andhra_Ikshvaku
https://en.wikipedia.org/wiki/Pallava_dynasty
Sinhala
https://en.wikipedia.org/wiki/Anuradhapura_Kingdom
https://en.wikipedia.org/wiki/Kingdom_of_Polonnaruwa
https://en.wikipedia.org/wiki/Kingdom_of_Dambadeniya
https://en.wikipedia.org/wiki/Kingdom_of_Gampola
https://en.wikipedia.org/wiki/Kingdom_of_Kotte
https://en.wikipedia.org/wiki/Kingdom_of_Sitawaka
https://en.wikipedia.org/wiki/Kingdom_of_Kandy