Firstly, congratulations for being brave enough to open up to your girlfriend about this part of yourself.
As many have said, the most important part of all this is clear communication. It's good that you're making a list of things that you're interested in exploring, as that will help guide your desires and expectations for future interactions. However, you obviously need to keep her expectations (and limitations) in mind, and the best way to do that is through shared discussion.
Start with something as simple as "I'm interested in sharing more of this part of myself with you. Would you be willing to explore that?"
As Ozbub correctly suggested, a gentle touch is required here, as she'll obviously have her own interpretations as to what you'll mean by this.
Start with the lighter elements of your list:
"I enjoyed cuddling with you when I was wearing in December. Would you be open to expanding that physical contact to include things like holding me?"
"I appreciate that you'll allow me to wear around you. How would you feel if I were to slowly introduced other elements, such as a pacifier or a stuffed animal? OR Would you be open to me leaving my diaper uncovered in the near future?"
Having looked at your list, these elements are the least likely to be off-putting or outright rejected at first response. Wetting, diaper changes, and sexual acts are another tier of acceptance/involvement, and should probably be left for another discussion once she has become familiar with these lighter additions to her involvement (especially as she has already expressed disinterest in wetting, and having diapers in bed - that may be where she draws the hard line.)
NOTE: Mattew made a good point of letting her know that there are others who share this part of you, so that she can better understand that this isn't as strange or upsetting as previously thought. But again, slow and steady wins the race...
Equally important (if not more so) is understanding her perspective on all of this; her reservations, her fears, her questions and her comments. Give her room to express these views in your discussion, and reiterate your appreciation for her involvement. Make sure she knows that you don't want to put here in a space where she is uncomfortable - and that if she is, you're willing to slow things down.
After you've expressed your desires, and she has expressed what she's willing to explore (and what she isn't), feel free to negotiate a timeline:
"I would like to have tried this by [insert agreeable date here]."
"I'm happy to wait [however long] until we started involving this part."
Of course, your milage may vary. I'm no advice columnist, so take all this with a grain of salt. You're the one who knows your girlfriend the best, so just take it slow, use open and gentle language, and hopefully things will work out for the best.
The best of luck to both you and your girlfriend, man.
TL;DR: Express your desires carefully, find where her limitations are, and sort out a timeline for all this to happen over. Communication, communication, communication.