Yes! You should be able to do this via Fusion. First, you would need to pull in the ID of that Requestor and then add it to the Approval Process creation module as shown below:
Approval Process Module:

{
"approvalProcess": {
"ID": null,
"approvalObjCode": "TASK",
"name": "",
"isActive": true,
"isPrivate": true,
"approvalPaths": [
{
"ID": "k10B5lJI0Il5JEZAbG00U",
"targetStatus": "INP",
"shouldCreateIssue": false,
"rejectedStatus": "$$PREV",
"objCode": "ARVPTH",
"approvalSteps": [
{
"ID": "5E4spdpQ8FAqV3I6F1qtK",
"approvalType": "OM",
"sequenceNumber": 0,
"objCode": "ARVSTP",
"stepApprovers": [
{
"objCode": "SPAPVR",
"user": {
"ID": "INSERT THE ID OF THE REQUESTOR HERE",
"objCode": "USER"
},
"userID": "INSERT THE ID OF THE REQUESTOR HERE",
"ID": "INSERT THE ID OF THE REQUESTOR HERE",
"approvalStepID": "5E4spdpQ8FAqV3I6F1qtK"
}
],
"name": "Test-Stage-1"
}
]
}
],
"objCode": "TASK",
"description": ""
}
}