Saviour Siblings

[DunderBlue]

I found out just before lockdown last year a person I work with was looking to try and have IVF with a "modified" embryo to be a saviour sibling to her child who has an illness that could potentially end up terminal.
I wasn't shocked to see it split my works with opinions ranging from the extremely outraged that someone would even consider such a thing to the people who said they'd do it in a heartbeat and wouldn't even waste time thinking about it.
At the time I said I agreed they should have a saviour sibling since they already wanted another child and if it would help save their baby then why not. But I wasn't a parent at the time and now I am I feel more confused about it. I know I'd do anything to save my child, but I also don't know if I could put another child through donating things to my first.
I'm not sure what my colleague ended up doing. She was looking at being approved for a saviour sibling, but I don't know if she went through with it. I know she had another baby (I saw on Facebook) but no idea whether it was conceived through IVF or if the new baby is a donor for the first child.
So my wonder is what are other people's opinions? In the black and white thinking I always thought it was a good idea, but now I'm not sure I could put a child through that. What is everyone's thoughts.

[TrainWhistleChoir]

My concern is what if the new baby isn't the saviour they thought? Or feels as they get older they were essentially bred for their sibling's spare parts. I can see the benefits for the parents and older sibling, but I think I'd prefer the genetic testing and tweaking to be there ahead of pregnancy one, to prevent the terminal condition to start with, rather than to grow a potential treatment with their sibling.