CoT isn't really CHA dependent, which is one advantage it has over Paladin/ Blackguard. 14 CHA is just fine...
Actually, 8 (or 6, depending on race) CHA is just fine for COT, one takes the class for the extra feats and saving throw bonuses. The special abilities are just gravy, and being 1 use per day are particularly marginal in a module with resting restrictions like Swordflight. They are nice added bonuses if you need high CHA anyway for some other class or special purpose, but it is a waste of ability points to boost CHA above the minimum just to use them effectively.
Monk is a one-trick pony, very boring and it's going to be shit in Swordflight.
I am not sure about that, or at least that it would be worse than any other Shifter build. Monk helps a lot on the AC front, allows one in conjunction with Zen Archery to fight somewhat effectively at range until gaining access to more powerful Shifter forms, and offers a bunch of miscellaneous benefits like Evasion. Though naturally going all in on WIS would offer more benefits to a build focusing a bit more on Druid spellcasting, or to one going for Dragon Shape rather than Risen Lord. Perhaps not what you are interested in, but I would not recommend against it if speaking more generally.
While I'd prefer to be evil I don't care that much. I don't know which would be better, though, DwD or halfling CoT...
Dwarven Defender is probably the best. DwD damage reduction on top of Risen Lord's Slashing/Piercing immunity will help your defense a lot. The only feats you really need are Alertness, Dodge, Toughness (class pre-requisites), Blindfight, Exotic Proficiency, and Weapon Focus & Improved Critical in Scythe, which I think you can fit in pre-epic, though you would need to take Dwarven Defender promptly at Lvl 12 since that is the only class that can take Weapon Proficiency feats. Knockdown is most useful to Sneak Attackers. I dobut Dev Crit is worth it here, with a Scythe you will be doing massive damage on crits anyway to mobs not immune, and f you forget about Dev. Crit you do not need Power Attack or Cleave, and in addition you can boost DEX for more defense rather than redundant STR. Also in Swordflight you can even be evil eventually. Start out as Lawful Neutral, and once you have the 5 Druid levels you need for Shifter (or however many Druid levels you want), start making choices that shift your alignment to evil, and just take Shifter and DwD levels thereafter. Perhaps take 5-8 Levels of Druid, 10 Shifter, and DwD for all or most of the rest.
If there are some extra feats you really want, or really want to be a halfling, COT can work too. You could even eventually use Swordflight's alignment changes to make an evil COT, though it would be more complicated with that class.
... So you are saying that it's basically up to me to decide whether I want to go DwD, Blackguard or CoT and each one will work for Swordflight?
Pretty much. Any of the three will likely be difficult, but any should also be playable.