I know of quite a few MTF crossdreamers who take hormones, even if they are not planning to transition socially and/or medically. Some do it to calm their dysphoria, others because they want to experience at least a part of having a woman's body. For many it seems to be another way to express their other self, in the same way crossdressing can be.
That should be OK, as far as I see it, as long as they have taken the side effects into consideration. For instance: It is best to have a doctor on board, even if you go for the herbal option.
I saw from your introductory message that you are doing this right now, and that you do it for yourself, and that you are no longer willing to deny yourself this exploration to please others. Again: We do what we need to do, and if your crossdreaming is strong this makes sense to me.
There are consequences, of course. Your body will be feminized and that will most likely be visible to others, at least if you plan spending time with others on the beach, in the gym or in the spa. I have heard of crossdreamers who have had to bind down their chest to present as male. They tell me that it is all worth the effort, but I am sure there are also those who find it all complicated. Breast growth is not reversible without surgery.
There is one more thing to consider. If doing this is a result of gender dysphoria, I suspect the urge can be the result of being transsexual. That means that there may come a point where transitioning becomes the logical outcome of the process. I guess it would make sense to keep that in mind before a crossdreamer embarks on this kind of journey.