This can be done. The question is whether there is a high purpose and whether it is allowable in terms of the karmic interplay that would ensue stemming from a change in the person’s life through such a maneuver? To what extent would it affect others in an adverse way or create a distortion through having some special advantage others cannot enjoy and the many ethical considerations in perturbing history? These are the complexities of time travel per se and this would be no different. Whether you travel physically through time and emerge at another point on your personal timeline or send a part of the mind back in time to deliver a message or a warning, the consequences could be identical and would have repercussions, so there would need to be careful planning, preparation, and consultation to define the purpose, the goal, and consider the pros and cons, and ideally have the blessing of Creator before undertaking such a mission.
A channeler could do this on their own without Creator’s help if there were a divine reluctance to participate and facilitate the communication. The question then would be to what extent there would be a karmic downside for the channeler in doing so? By taking something for themselves that in the past did not happen, the question would be, does this put others at a disadvantage, would they lose out in some way? So there could be a benefit obtained in the short run but that would likely be followed by a negative karmic consequence, and so the exercise would not be a benefit in the long‑term despite its attractiveness in thinking about it superficially. But, again, the possibility is very real. This can be done and would have the same potential practical limitations in whether the message would be absorbed, taken to heart, and acted on or not, that would continue to be a variable.