Killing aside, your three other solutions are even more risky than severing them and holding them.

The Light has zero garantee that there's not another binder somewhere (and doesn't know if one binder can undo what another has done. LTT would know this, though, as well as how to properly use them!), but even if only the same binder must be used to to remove the oath, a binder can be stolen.

An a'dam can be removed, and if it happens you get a Forsaken at full strength on the lose... like Moghedien...

Compulsion is hardly full proof, and I wouldn't like to see what Graendal might do with a compelled "neo Dreadlord" or Forsaken. The only compulsion we've seen hold are the one used by Graendal, on a regular basis by Rhavin, or by Moghedien when she was holding a net. Everything else we've seen, especially when it went against the deeper nature of someone, has fallen apart eventually.

Killing is an option at the moment, the main option. It's of no use to interrogate though, and we know it's not the best solution since a fair amount of balefire aside, if you kill a Forsaken it's near disastrous: no only he/she could be back for TG, but at full strength and in a new body. Lanfear as Cyndane could stand right at Rand's side for days, and without Cadsuane/Nynaeve and their gizmos, she could go completely undetected.

Severing allows all Cannoli pointed out, and if you combine it with hiding and holding the person well, the Shadow is screwed. The severed Forsaken would have to be found, freed or killed by the shadow, then perhaps would neeed Healing even with transmigration. Right now, Flinn's the only male able to do it, and perhaps the only man to know how. Demandred, Moridin and if you insist Taim would stand good chances of being healed at full strength, but who would heal Semirhage, Mesaana, Cyndane, Graendal back at full strength? Demandred or Moridin? The only Forsaken who might know how it's done is Osan'gar, and without the skills to achieve it, only to explain, maybe.

Assuming that the Light finds out about transmigration, a solution might be severing coupled with stasis (assuming LTT knows Sammael's trick) and hiding the person well - but it's all assuming a Forsaken can't be tracked down by the like of Shaidar Haran using the DO's mark, and it's not exactly a bet I'd take after he popped up with such accuracy in Mesaana's meeting, at Sammael's meeting with Sevanna - not hard evidence, but suggestive.