A knight/rōnin armor frame.
Since we got 2 health frames and 1 shield frame it’s only logical to eventually have a armor frame. Understandably it would have no shields, low/medium health and A LOT of armor so that it would make up for the low amount of health.
Visually it would look a knight.
Their signature weapons would be a sword and shield (melee) and a crossbow (primary or secondary)
If a quest is possible to have with it then...: it’s a story about letting go of the past. The operator (who’s a ghost) of this frame is seeking redemption for a duty they failed to commit to long ago by protecting orokin information from falling into anyone’s hands, which they desperately hope would bring any surviving orokin to them so they would give back their lost honor. In the end we would’ve helped them come to terms with what had happened and that would let them pass on leaving their warframe in our care.