Somehow, I managed to miss Say'ri's B-day even after posting about it. -_-;
Anyways, keep a close eye on your wallet as today's Severa's B-day.
Severa is the series second female to start as a Mercenary since Malice from the BSFE chapters (if you don't count FE5's Machua since she needs to promote into the class, also New Mystery retconned
Malice Maris into a Myrmidon so she doesn't count either). Her only in-game consideration is that her recruitment chapter may necessitate a Rescue Staff use or two depending on the difficulty level and your units' mobility/efficiency.
Personality aside, Severa is probably the hardest child character in the game to screw over outside of Morgan given her mother's spectacular inheritance (i.e. the Mercenary, Pegasus Knight, and Dark Mage class trees). If The Avatar/Morgan didn't exist, this alone would be the best standard class combination in the game. Skillswise you have Armsthrift, Galeforce, Tomebreaker, Sol, Bowbreaker (for the flying Peg classes), Axebreaker (which goes great with...), Vengeance, Patience, Anathema, Slow Burn (I guess), and Lancefaire (which is only useful on her Pegasus Knight classes at base; and Bride if you want to count that) which is a solid set but the real reason why these classes are awesome is that Hero and Sorcerer are top tier classes for physical and magical characters statwise respectfully, losing out to only Paladin in terms of meeting/exceeding stat cap averages for a base class (and Paladin only wins because its mounted). In fact, only Dark Flier and Bow Knight are really not that great stat cap-wise for her.
That said, Severa's biggest issue is getting enough Magic together to use her Sorcerer class since her mother is one of the few mothers that isn't magically biased growths/cap modifier-wise (she might be where you'll end up funneling your Spirit Dust towards). Speaking of stat cap modifiers, Cordelia's modifiers primarily boost Skill and Speed with a small boost to Strength for a hit to Magic, Luck, and Resistance for an overall average +2 stat cap modifier total. As a child character, this means that Severa will have large boosts to Skill and Speed, a solid boost to Strength, and a minor boost to Defense before her father's modifiers are applied.
And on that note, the only potential father that can give Severa all nine possible classes as inheritance is Kellam, who is actually one of the better choices for her (even if he only gives her a +1 total modifier) since the Cleric, Knight, and Thief class trees gives Severa a ton of alternate roles and he gives her a large +3 Defense boost and minor +1s for Strength and Skill for hard hits to Speed and Luck. Cleric provides Sage for Tomefaire to make her Sorcerer class even better and War Cleric's Miracle and Renewal for even more health regeneration/survivability options beyond Sol/Nosferatu/Aversa's Darkness. Add in General's Pavise or Great Knight's Dual Guard+ and she'll turn into a brick shithouse (with Tomebreaker adding in some extra Magic Defense). Alternatively, Trickster's Lucky Seven will greatly compliment her other +Avoid options and Move +1 isn't a bad skill either if she wants to default back to Hero, plus both it and the Cleric class trees will give Severa more time to build her Magic stat up if you don't feel like roiding her up. Also Great Knight's Luna is there for some added offense rather than relying on Vengeance's lack of a boost due to Severa pretty much never having an HP deficit around long enough to make use of it.
Her other top choices for father would be Ricken (great Magic stat cap modifier to aid Severa's Magic and access to Mage, Cavalier, and Archer classes for Tomefaire, Magic +2, Aegis, Luna, Dual Guard+, Skill +2, and Hit +20 for Bow Knight and Dark Knight overlap, hits to Strength and Defense modifiers, and a measly +1 modifier total), Virion (solid +2s to Skill and Speed cap modifiers and access to Mage, Wyvern Rider, and Archer classes for Tomefaire, Magic +2, Quick Burn, Deliverer, Swordbreaker, Lancebreaker, Strength +2, Skill +2, and Hit +20 for a massive hit to the Defense modifier and a minor one to Luck and Bow Knight overlap), and Stahl (fantastic physical stat cap modifiers with a +3 total and access to Myrmidon, Cavalier, and Archer classes for Swordfaire, Astra, Vantage, Aegis, Luna, Dual Guard+, Avoid +10, Skill +2, and Hit +20 for Bow Knight overlap). Her worst father option is either Donnel or The Avatar as Donnel only offers Severa three classes (all within the Troubadour class tree) which aren't bad in of themselves but other kids want him far more and the same goes for The Avatar.
The tl;dr for Severa is that she is practically guaranteed everything she needs to rock right out of the gate. Her only drawback is that she's not male and thus cannot access the Dread Fighter class for the incredible Aggressor skill. At least she can work as a Rallybot if all else fails with Rallies Speed, Movement, Love, Skill, and if sired by Kellam; Magic, Defense, and Luck.