I think Vampires in the Sims 4 are almost the best they could possibly be but a couple of things could be added to make them better.
1. I wouldn't mind them to have a scary aura in fact I think Vampiric auras could come in a couple of types. For example Scary, Regal, Morbid. This could be something they add to the Vampiric Powers you can choose.
2. They just need a couple of new powers
Walking down walls
https://www.youtube.com/watch?v=-lucrJmdbi0
The Rats at the 1 minute mark
https://youtu.be/mzyeGBdQmCM?t=71
Levitation
https://youtu.be/eC5HZzjjI9Y
I'd love the Summon Eclipsing Fog as a Vampiric Power
http://simscommunity.info/wp-content/uploads/2014/10/ts3_weatherstone_fog.jpg
Homicidal Shadows
https://www.youtube.com/watch?v=pzeqvq4lFeU
http://www.dreadcentral.com/wp-content/uploads/2016/04/nosferatu10.jpg
Leaning over a Sims while Sleeping
http://3.bp.blogspot.com/-ITcVtiIhqJ4/T7JWRu6i9bI/AAAAAAAACCw/Z5xgoODazVo/s1600/Nosferatu+11.jpg
https://iconicimages.net/app/uploads/2019/10/NosferatuNewsHeader.jpg
http://4.bp.blogspot.com/-GKyqqEDuAjQ/ThW4wxyBy6I/AAAAAAAAAZ4/0iYYOTU2Ycs/s1600/BELA3.jpg
3. Vampire dueling Witches. I would love to have Witches and Vampires fight. I think it would be pretty wicked to see. I think it could be just a small tweak to give them dueling type powers based upon the traditional Vampire skill set. I know that there is a brand of magic in Fantasy called blood magic maybe a fw ideas pulled from there.
4. I think these New Lots are definitely in order
Cemetery and Vampire Night Clubs for Community Lots
http://i876.photobucket.com/albums/ab325/petalbot/sims%20vision/grave.jpg
https://i.neoseeker.com/screenshots/MjAxMi8xLw==/the_sims_3_supernatural_image_a4oBn.jpg
https://orion-uploads.openroadmedia.com/lg_819ba5-HighgateCemeteryHighgateVampire_tombs.jpg
https://live.staticflickr.com/3290/3063362698_6bf14ef9ae_b.jpg
Thank You Mod the Sims for the picture
http://thumbs2.modthesims.info/img/7/4/2/6/5/5/MTS_ruthless_kk-1151597-VIP-area.jpg
http://simscommunity.info/wp-content/uploads/2014/05/Bmgz1lbCEAAFt9Z.jpg
5. Pet Bat Pictured is not a Vampire bat but one of the cute Flying Foxes
https://i.pinimg.com/originals/1b/f7/bb/1bf7bbfde7b5c2fe9e029b6f47cc109a.jpg
https://i.redd.it/t6kd8apdavj41.jpg
6. Plasma Fruit Bath
https://thumbs.modthesims2.com/img/1/7/5/4/7/1/MTS_gwillewyn-385606-BloodBath.jpg
Coffin Tub from Sims Freeplay
http://4.bp.blogspot.com/-XVQaMBTp0Wk/U8XYhW0H0GI/AAAAAAAAAbk/dzMzsV45xd4/s1600/IMG_0247.JPG
7. A few things to make their homes a bit more scary. Because if their homes cannot look scary and imposing neither will they.
Vintage Vampire Bat Illustrations Framed - Just for a bit of ambiance
https://i.pinimg.com/originals/79/e6/ef/79e6ef2ea4b685a230b40cea34f8a2c0.jpg
More Gargoyle Decor
http://i.imgur.com/wNITX.png
http://thumbs.modthesims2.com/img/4/5/5/0/5/MTS_gromit-122444-GarDeskPrev03.jpg
Now that is a fireplace in a vampire's house
http://m.cdn.blog.hu/th/the-sims-freeplay/image/img_0654.JPG
The Sims 3 Store's Gothique Collection had several wonderful decorative pieces that would be wonderful in a Vamp home.
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/sculptureGothicGlassSpider/Thumbnail_300x300.png
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/fireplaceMantleGothic3x1/Thumbnail_300x300.png
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/clockGothic/Thumbnail_300x300.png
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/paintingGothic/Thumbnail_300x300.png
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/mirrorWallGothic2x1/Thumbnail_300x300.png
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/lightingFloorGothicCandleStool/Thumbnail_300x300.png
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/bookshelfGothic2x1/Thumbnail_300x300.png
Sims 2 had the best coffins
http://thumbs.modthesims2.com/img/1/7/8/7/2/MTS_zedrik-128873-coffin_darkgreen.jpg
Bat Houses
Victorian
https://www.yardenvy.com/images/pz/23874/Heartwood-010B-Victorian-Bat-House.jpg
Modern
https://image.sportsmansguide.com/adimgs/l/7/721264m2_ts.jpg
Castle Build Pieces
http://www.anelnoath.com/butterdrac5.jpg
https://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/WindowCastle/Thumbnail_300x300.png
http://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/sculpturecapcastletower3x3/Thumbnail_300x300.png
http://na.lvlt.sims3store.cdn.ea.com/u/f/sims/sims3/sims3store/objects/doorDoubleCastleThin/Thumbnail_300x300.png
http://s0.geograph.org.uk/photos/46/97/469741_ca885dbf.jpg
http://www.scifimoviezone.com/imagehorror/dracula92017.jpg
https://community.gamedev.tv/uploads/db2322/optimized/3X/b/7/b7f9bd2686140ad9d4fac07c6e9a2709c4465d3d_2_1024x656.jpeg
https://c1.staticflickr.com/1/141/337570569_11092d4d7f_b.jpg
https://render-state.to/wp-content/uploads/2019/08/i13Drawbridge-788x1024-1.jpg
https://external-preview.redd.it/bs5Cj_jP4hs1Ht-kVmDR0MazHtAQjtcmt2ai17wIRUg.png?auto=webp&s=79d476db785e6af8ad9d0b46f6906f52231f92f6
Castles should also have equivalent fireplaces
http://thumbs.modthesims2.com/img/6/5/4/3/7/8/MTS_TheJim07-1757726-02.jpg
Moon Phases
http://holyhiway.files.wordpress.com/2010/07/8_moonphasesw.jpg
8. Vampire Manicure
http://media-cache-ec0.pinimg.com/736x/e9/7b/9b/e97b9b75564c3694f2497da393d0da1e.jpg
https://images.totalbeauty.com/content/photos/17-totalbeauty-logo-bewitching-halloween-nail-art.jpeg
9. Finally some of the vampires lore has them having an awful smell coming off of them mostly from their breath. Perhaps foul breath could be a weakness
https://s-media-cache-ak0.pinimg.com/736x/2e/ba/ca/2ebaca7d4becc128f15ed659e62533b5.jpg
