This falls into the category of altering the intention of those launching prayers forth and we have told you previously that this cannot be done, it must be done by the originator of the prayer themselves. So despite the fact this has appeal, because so many prayers are a onetime thing, for example, and are often a recurring request but sporadically, and then the issue that many people over the years will chime in at intervals of their choosing to launch quite similar prayers for a quite similar purpose as there are perennial human problems such as war, times of social unrest, famine, etc., so to gather all like prayers together and make those a focus of the Lightworker Healing process to then have them repeated in perpetuity seems an attractive notion, would that it were so.
Unfortunately, once people make a prayer request and it is launched forth, it cannot be borrowed and built on by anyone else to suit their own purposes or way of doing things even to magnify the intention of the requester originally which is really all you are saying here. Not to use their prayer energy for another purpose of your own but to make their prayer and their intention more effective. Unfortunately, you cannot speak for them in their absence in this way because it is, although well-intentioned, overstepping the boundaries of their free agency and free will to do it without their knowing.