Synonyms for Opine:

n.

express, formulate, state, articulate, remark, pronounce on, air, be of the opinion, opinion, deem, hold. opine (noun)
imagine, animadvert, guess, think, suppose, reckon, speak up, sound off.

v.

comment (verb)
observe, animadvert, reflect, express, state, remark.
figure (verb)
think.
imagine (verb)
brainstorm, suppose, consider, conceive, design, imagine, envision, create, invent, theorize, ideate, plan, contemplate, perceive, observe, fantasize, think, reflect.
opine (verb)
suppose, imagine, conceive, guess.
suppose (verb)
brainstorm.
surmise (verb)
consider.

Other synonyms:

deem. hold. Other relevant words:
formulate, animadvert, state, deem, be of the opinion, sound off, air, hold, speak up, articulate, opinion, remark, guess, reckon, express.