Is Caeda good for a merge project candidate?

Yes, she would be a powerful unit to invest in. Her weapon refine makes her very useful. Also, if you ever decide in making a flyer emblem team, she would be a good sword unit to fill that role. She is also very easy to Merge to +10 if you're going for that, because of how easy she is to get.

Well, I would say yes, Caeda is worth pursuing. Although her attack stat is pretty low, she can easily make up for it depending on how you build her. I'll give you my Caeda as an example. Her attack is still relatively low, but with speed that high and a Res stat that high in combination with her Wing Sword special trigger effect for activating specials quicker as well as doing bonus damage to Armor and Cavalry, she can dish out some serious damage, even without buff flier emblem buffs. She also makes a fantastic magic damage tank.

The ivs I have on mine are -spd / +Res. I would prefer -def / +Res, but for now it's fine. Mine is obviously built for Flier Emblem team, but with Res that high without additional combat buffs or Rally effects, she can easily run Ploys and debuff the crap out of most units in the game.

My last point would be that she is pretty easy to come by since you can role her as both a 3* and a 4* which makes her relatively easy and reliable to merge up to +10 if you were to ever want to go that far with building her. I actually plan on +10ing mine at some point in the future after I finish some other units I'm working on.

Caeda rocks. Especially on a flier team. I run her with distant counter Myrhh, firesweep cordelia, flying azura. All 4 have goad flyers (+4 atk/spd) so shes consistently getting the +12 boost in each stat, which puts her at 56 atk / 55 spd. Throw in ally support woth myrhh for another +2 each stat, then the seals of your choice... Beast.

Caeda is a great unit. Her attack really isn't as bad as people say it is, but she's going to struggle a bit against anything that isn't green, mounted (cavalry), or armored unless you're stacking flier buffs on her. (Given that so many people like spamming armors, you have a good case.) atk boon and wing sword give you 45 atk, if I remember correctly; if you run fury that puts you at 48, which is serviceable. If you go for swift sparrow her physical bulk will be awkwardly thin for a melee unit. She can work in a mixed team, but fellow fliers are what can turn her into a monster. She can even run a galeforce set thanks to the flashing blade refine on her weapon, so she can be really fun.

The main problem I would see for your trio is Myrrh, who shuts down your speed with Great Flame, or a really high def Fae (I've seen people push her def almost to 40; def boon + steady breath + def refine on breath put her at 37 without merges, so if the chicken adds close def and you run fury without buffs you're striking with 57 on 43 and not even a special is going to cut through her). A.Tiki will be problematic if Nowi can't deal with her, but generally I find A.Tiki so slow and low enough in res that Nowi won't even need investment into her speed to two-hit KO. Y.Tiki...not so sure. You might cut through with an iceberg/luna/moonbow, or you might not. In these matchups at least you are at a stalemate; the dragons will find themselves walled by her res so teammates are going to determine the outcome.

You might like to consider Marth. He can't reposition people over mountains or destroy armours, but he can heal (or run swordbreaker if Falchions are a concern, but he can be set up to natural-double most of them), he gives +2 to all stats and +3 or +4 to two others (depending on drive or hone/spur) so your teammates become monsters, and he'll rip through any of my aforementioned concerns. You might run into issues with really high def Hector trying to vantage bonfire you, so he's not without his struggles.