I would say you have already received some good advice. Accessories are one of those things that you either really want or don't feel are necessary. I don't think you would go wrong getting any of them.
As one who didn't/doesn't have most of these accessories, I will give my perspective.
1)
Bumper - Ours doesn't have a bumper. It wasn't an option when it was built. I don't foresee us putting one on,
HOWEVER, if ours had a bumper on it when it went to Alaska, it wouldn't have received the nice dent that it sustained in the roll pan when it was backed into a post. (BTW...it wasn't us who did it.
) You won't see a dent in it today, as Craig removed it when he did major renovations on the tear a year ago. So, yes, a bumper is nice & for some, a necessity.
2)
Screen Doors - Screen doors are the one thing I would pick over any of the accessories you are looking at. This is another accessory which wasn't available when ours was built and because they used a different door construction & trim, screens could not be retrofitted to our tear. Our first teardrop had the "early" version of screen doors. They were made by me, in desperation, when camping for a week by myself with the kids, in humid, northern Wisconsin, in 104º weather, with lots of mosquitoes (also no fan or AC, as this was the early days). I went to Wal-mart & bought netting & sticky backed rolls of Velcro. Worked fine in a pinch but not very durable in the long run. I am delighted to say, that as a result of the renovations on our tear, new doors were installed, which allowed us to add the screens. I am truly a Happy Camper!
3)
Wind Screens - This is a newer accessory, also. All of our customers who have these love them. Again, we don't have them mainly because for us, crosswinds haven't been an issue.
4)
Second Side Tent - Again, one of those things where our customers who have a second one, love having it. We just got a side tent a couple of years ago & use it when we need it (camping trips where we are staying longer than a weekend, or when it's rainy/snowy, or in places where we want more privacy). A second tent is useful if you have dogs, a porta potty, and/or kids. Or if two of you each like your own dressing room.
5)
Water Heater - Also one of those accessories that those who have it love it. We don't have one but on occasion, it would be nice to have hot water on demand.
Like I said previously, you really can't go wrong with any of them.