If a publisher trusted that YSNet could get a decent return of a 20+ million investment, wouldn't S4 have been greenlit as soon as S3 started rolling in money? YSNet hasn't proven it can make a lot of money when the stakes are high, it has only proven that it can make a niche open-world game that might break even, which is surely the whole reason S4 hasn't been announced. If S3 had made a bunch, SEGA would be bankrolling this thing.
I'm not criticizing their achievement with S3 (I love it for all its faults), but if YSNet's ability to make a kickass mainstream title out of S4 with Suzuki's desired budget wasn't considered risky, they wouldn't be making smartphone games.....
Not sure this argument supports the theory that YsNet are making a new IP with 110 instead. I'll explain what I mean:
Shenmue is a known multimedia IP with a recently released instalment. If turning a profit is the sole deciding factor in whether the game gets funded or not, Shenmue is still a safer bet than a new IP without any existing code base to work from.
Wanted: Dead is a new IP, but it's trading off the pedigree of the Ninja Gaiden series in its developers and genre roots, and Soleil has previously developed hack n' slash titles.
Both are more financially sound investments than a new IP in a genre a developer has no recent history in.
Secondary point; why would a theoretical Shenmue IV come from 110 and not SEGA or Deep Silver? It's reputation vs return.
110 are a new publisher looking to build a reputation for themselves as champions of Japanese developers and fans of genres that were around during the sixth generation of consoles. They still have to manage risk like any other profit-making enterprise (detailed above), but there's more for them to gain than cold hard cash right now, and Shenmue would be a major feather in their cap.
SEGA and Deep Silver are the opposite. They're established, you know who they are and what they do, they're sat on a number of recognisable IP, and they are publicly traded companies. They're interested in maximising returns. Maximising is the important word there because that's why they would pass on projects that would break even or make a small profit.
This is why, for example, SEGA are chasing the "games as a service" multiplayer shooter trend with something like Hyenas rather than paying for a passion project like Shenmue. You can see a similar trend in Hollywood where small/mid-budget movies have been abandoned by the studios while they chase big shared universe hits. Everybody wants to be the next Star Wars, MCU, Fortnite, etc.
SEGA/Deep Silver and 110 want different things for their businesses and will subsequently pick different projects.
As for Air Twister, I feel you're mischaracterising a side-project that came about as a result of a meeting between Yu and Apple. We're not in the Shenmue Gai/Shenmue City era of YsNet at all anymore, thankfully.
There are reasons why a YsNet/110 collaboration might not be Shenmue IV, but I don't believe giving them a dry run with a new IP in a genre with no recent experience/technological base is it, because it's antithetical to the purpose of giving them a low risk project in the first place.