You want to do more spying with your crows?
I'm guessing that you've already taken a look at the 136-150 period for Adelbert? It started with the Aviary of the Watchful Covenant two posts down from the post I linked, I spent a fifteen year period developing tools for gathering information and projecting magical power mostly through magically created and controlled crows. The character was more than 100 years older than Corvus at 31-45 but there might still be some inspiration in there.
Still Corvus has got crows that posses reasoning minds and the ability to control them. He's got a great number of tools to get his little darlings to spy for him, and now he's got tools to let them kill for him as well.
I don't necessarily want Corvus to travel down a similar path to Adelbert but being able to open up intangible tunnels to your crows to let not only Corvus but also the rest of the magi throw their spells all over the middle east sure would be convenient.
Crows that are large enough to haul freight might be nice, or alternately develop some magic where you transform anything that you wish to move into a flock of ravens, and then your cargo flies itself to the destination of your choice and turns back into the original stuff. That second option would be amazingly mythic.
Along the same lines how about turning a pile of rocks and logs into a flock of crows, having them assemble themselves into a structure and then turn back into rocks and logs but now they're a building. That would be near impossibly difficult, it's totally something a magus should devote themselves to
Invisible crows are simple thing for him to work out at this point. he could do iron plated steel clawed battle crows that would be simple and fun, but you've already got a whole bunch of battle magic. Is there a way that you could have the crows deal damage to a target in a way that bypasses magic resistance? Something like giant ravens dive bombing with rocks, or something more dangerous.