TL:DR The Abindon are evil and allow Cradle to be a Soul factory which slaughters the innocent and produces recruits from humanity's cutthroat and power hungry.

Could Suriel not simply whisk Lindon away and endow him with power? We know elixirs exist that could take someone from Bronze to True Gold even on Cradle. Higher stages require deeper insight but the Presence machines are capable of giving you leading you down paths of knowledge in an instant, so given that it's at least fairly likely the Abindon have elixirs and insight capable of raising Lindon to at least a Monarch level... Why not just extricate him from Cradle?

Why have the Cradle recruitment engine at all?

I guess they can't intervene with Fate or the Way and The Way has willed certain things, but that ephemeral force of destiny certainly designed a pretty savage universe.

If she doesn't take him from Cradle because she wants Lindon to get stronger himself... I guess there's certain merits to that. Suffering toughens him but he'd already known sorrow and understood the consequence of weakness and he was as selfless as his world would allow. I'd argue he was ready to leave Cradle right when they met.

Does Suriel send Lindon on a less than righteous Odyssey in pursuit of raw power, risking an already noble moral character? All this is further complicated because Suriel herself doesn't seem free of the brainwashing and necessity to advance as a hierarchy exists even at her level.

Is the true test of Cradle to rise through advancement while maintaining morality? TONS of ramifications if that's the case involving free will and the Cradle engine itself. Christian parallels everywhere.

I think the most damming thing is that good people die every day on Cradle missing out on a readily available immortality in a society that's outpaced scarcity.