Quirky makes a good point where he mentions that “at the general meeting, it is possible to amend the motion”.
He advises that some legwork ahead of the meeting will be needed, in order to get the text of the motion right.
Anyone not just the proposer can at the meeting offer to amend the motion, but it would help for the proposer of the amendment to discuss the changes before the meeting with others.
Alternatively, the person proposing the motion (as listed in the agenda) can also withdraw it a general meeting. I have seen this done numerous times for various reasons.
Withdrawing may be a popular decision because that will give everyone time to come up with alternative text for the motion, which could be considered at a future general meeting.
Nobody gains by amending on the hop, especially when holes in the listed motion are shown to be large enough to drive a tractor through.