Non-Destructive Webhook Ingestion: Mapping Fields Without Data Loss

It would be amazing to be able to non-destructively add a webhook ingestion source mapped to specific columns. E.g,. if I have a table taking values from multiple sources and I add a webhook source. If I were to map a field from that webhook to an existing field (e.g., first name), mapping it for the webhook will erase all the non-webhook values. This means that if you have more than one source, you (unless there's another solution I'm not aware of) you'd either need to have helper tables, or helper columns (e.g., First Name Source 1, First Name Source 2, First Name Source 3, which then map to First Name Final, or something like that)