And that's fine. I do what I do because I have a mentality of non-fungibility. There aren't simply more fish in the sea, this is my person. There's not another one out there for me.

There isn't anything ethically wrong with someone with a more flexible approach to romance or someone who has a hard boundry. Not everyone is down for a sacrifice at that level for another person - and that is okay, not everyone is deserving of being the recipient of that kind of sacrifice just as everyone isn't nessisarily capable of making that kind of sacrifice. If you are only kind of happy with your relationship then that's not enough it has to be deep. It isn't nessisarily easy, it doesn't get easier and it might require daily conviction. It is a vulnerable space too. If you don't have absolute trust it's not going to work and absolute trust comes with intense emotional risk.

But on the other hand of things if your partner is dead set on doing this, you love them in a holistic way, you're in a stable environment and you are at any level unsure of your ability to be attracted to them... you could probably afford to try. You might actually surprise yourself with be how you are okay then you thought you would be - and you can set the expectation at the beginning of the process that you are unsure of yourself and don't know if it's something you can do so they know and weigh the risks as part of their transition. Not all transitions are 100%. Trans people are often very calculated about what they choose to pursue based on what they personally value out of life in a more general sense. Not everyone goes for every option and the reasons behind them are intensely personal value judgements that involve way more than just the dysphoria/euphoria hits. I think way too many people peace out of things in general before they try or fully understand something and miss out because they built molehills into mountains. The process of transition isn't lightning fast. You have time to think, to adjust, to compromise and if it really isn't working for you then you will be absolutely sure that it's not for you.

It all depends on your personal estimation of the value of the relationship you have going and how open you are to the process of self exploration to test your hypothesis about yourself against an actual real life situation. Because none of us know ourselves half so well as we think we do.