I definitely relate to what you're talking about. Even when I have used a fantasia on my retainers, I don't use the same name and their previous employment to me effectively ended at that point. With that in mind, using a fantasia on my own character is absolutely unthinkable as I feel like I would essentially be killing off my character.

I'm starting up a Viera alt come ShB. I was going to start her up early and start getting access to stuff and then just use a fantasia, but clearly I have a thing with getting attached to the characters I create, so I chose to wait. While the features you are suggesting would be nice, I am actually looking forward to going through the MSQ again as not all of it registered and was committed to long term memory.

The 'linking' between the two characters is going to happen through their lore. My Viera isn't going to be a WoL like my main, but will possess the Echo. Most of what she experiences via the MSQ isn't going to be what she personally does, but rather projections of the past made possible through the Echo. She doesn't understand why she's getting these projections, and just knows that she must pursue and seek out the WoL.

Even though I have to grind through the levels and the content again, what is going to help with that and making her own path is taking on new jobs and acquiring different soulstones I currently don't have with my main character. I'm a healer main now and focus on SCH and WHM, with DRK as my tank; my Viera will be ranged DPS with focus on DNC and BRD and will likely have WAR as her tank. I am very much looking forward to writing up the lore for the link between the two!