Strong 5* with Bloomed Forms and good Abilities:

Oncidium, Evening Primrose, Lantana, Camellia, Justicia, Toad Lily, Edelweiss, Leucocoryne, Lavender, Chocolate Cosmos etc.

There are also some strong 5* without Bloomed Forms:

Cymbidium, Dahlia, Cyrtanthus, Peach etc.

Dipladenia isn't a bad choice either cause she also has a Bloomed Form and like you said: Her Ability is usefull and a rare Ability as well.