[thanatropism]

It's not that difficult to compute true marginal effects from logistic regression using something like the bootstrap (if you have a distribution for your coefficients) or explicit differentiation. Every traditional stats app (Stata, SAS, etc) has this.

[claytonjy]

What do you mean by "true" marginal effect? Are you suggesting a post-hoc procedure can correct estimates such that they are close enough to the estimate that would have been produced with a more complete model specification?