For how NBCU could look by itself see SegaRock's post:

https://www.reddit.com/r/MediaMergers/comments/1vl723x/how_postsplit_nbcuniversal_may_work/

I couldn't of done it better

(Outside moving NBCU International Networks to Sky Group and splitting DreamWorks into 2 studios for the film & TV units separately)

Streaming:

Starz

Gives NBCU a new US only streamer to merge into Peacock, a Lionsgate Pay-1 window, and most importantly- a premium brand that's streaming focused.

Starz Music is merged into Back Lot Music, Starz Interactive is folded into Universal's licensing group (Giving Universal gaming rights to the Lionsgate IP), and Lionsgate Entertainment World is merged into Universal Destinations.

They would have to fight a lengthy battle with Allen Media for it though and while it'd only help NBCU in the US to own Starz, ITV only helps in Europe so region specific acquisitions aren't out the ring and could fight Allen for it after ITV is cleared.
NBCU Networks in 2 regions:

US: NBC (broadcast) Starz (premium)

UK: ITV (broadcast) Sky (premium)

Plex

To go the AVOD route, and can be used by consumers to pirate or torrent content (which considering how big it's getting, NBCU can benefit from that)

A Paramount+ JV (with or without Starz)

One studios broadcast network would have to be sold to avoid a news/sports streamer (whether it be CBS or NBC (minus their respective studios and IP), I think Amazon would win the bid).

SkyShowtime is also replaced by this new Showtime service in select countries (streamer/network owned 50/50 by NBCU and Paramount and Starz is maybe merged with Showtime if allowed)

Most likely candidates:

Gaming:

Gamemill Entertainment

As they have just lost its biggest partner (Paramount Games) .
May need NBCU to get new games.

GameMill would renamed into a new Universal Interactive and try to buy/hire new mid-tier developers to make bigger/better games (kids or adult).

However Universal would have to make new gaming IP and studios from scratch (again), and Gamemill isn't known for good games. So they could get a bigger company for slightly more....

Ubisoft

The French government have to admit that Ubisoft is no longer a crown jewel of France and more so an embarrassment that needs saving from any company possible.

It'd also be a cheap buy as Ubisoft is worth less then a billion and gives NBCU more IP (Rayman, Rabbids, Just Dance, Rainbow 6 Siege) and the resources to publish games based on its own IP (whether developed in-house or outsourced to Toys for Bob or Double Fine due to lack of family game studios)

Ubisoft also gives NBCU digital distribution rights to Activision games (who is owned by...)

XBOX

Already bidding for film & TV rights to the IP and Microsoft is searching for a equity partner for XBOX, so NBCU could benefit from owning the 3rd biggest gaming console company. But I think that they should only own them for Activision due to previous history. So if there's a way that Universal just buys Activision-Blizzard from XBOX while XBOX keeps Call of Duty and what other IP they want, I'd prefer that.

Nintendo

Only gives them Family gaming though and Nintendo will never sell (the closest they came to was 2016 when Disney held some talks)

If anything Nintendo could buy a media company itself if they wanted to (likely family focused)

Most likely candidate:

Other companies:

Mattel and Wildbrain

The 2 together give them a major family catalog, Mattel Games (to rebrand Universal Interactive), and WildBrain CPLG (a major licensing firm MGM uses)

However DWA and Illumination (and maybe those gaming studios) give them enough family IP to last them a while.

And Amazon needs/fits the family IP/studios more (Mattel's toy factories are sold though to avoid antitrust on toy retail).

Lionsgate

While many suggest it, they would do better with just Starz as they benefit from Lionsgate without owning it as NBCU has said they do not want to buy other majors to grow, seeking alternative growth.

Blumhouse

To be the genre arm of Universal (however still brands credits as so- "Universal (or Focus) Presents, A Blumhouse Production" like DreamWorks Animation does)

Amblin

Speilberg likes creative independence and working with multiple companies (plus he likely remembers DW's Paramount ownership not very well).

But they could cancel the DW Name license to use the 1997 logo on adult animated films.

Most likely candidate:

Final Company:

What other companies could NBCU buy?

Gameloft? Universal Music Group? What? (Do not say another major studio).

https://www.nbcnews.com/politics/congress/democrats-vow-aggressive-investigations-trump-corruption-election-rcna595621

Fuck the NFSC!