I have two Sonyas. I maxed one (and gave her emblems) long ago when she was my best blue. I leveled the costumed version of the second Sonya more recently (no emblems, as Telluria now greedily gets them).
I like Grimm (also maxed) but prefer Sonya’s speed and for a while I seemed to face a lot of Boril and Cyprian in raids and her dispel of buffs is very handy. The two of them together (Grimm and Sonya) are good against Titans – not sure how Titan’s figure in your question since you didn’t mention it.
Note that Sonya with Costume dispels status ailments. That increases her utility, IMO) since she can either dispel enemy buffs or ally ailments).
Given that you have Vela, I would recommend maxing a second Sonya. Her tile damage makes her a better supporting hero in raids (versus Richard) and her special is more impactful, IMO (again, versus Richard’s attack down).
In addition, if Telluria is your tank, you’ll likely flank with a red which puts blue on the wing, right? On defense, that’s likely Vela or Sonya due to their speed, right? Not sure what you have in mind there, but Richard seems to make more sense as a flank.
Finally, Richard will consume more materials and thus a 4* hero will be ready to appear in raids and wars more quickly than Richard, I suspect, unless you have a stock pile of food and feeders. But, given you have the scopes already (a little jealous there as I have Vela at 3.70 until a scope appears in a rare quest next month), maybe not.
He’s not a bad choice, so it’s a good problem to have.