To minimize headaches, you'll want to break up the consoles between the viable input methods (Composite, Component & HDMI) & then using input switches to help consolidate consoles that need to go through a specific input.
The XBox One, Wii U & Switch will want to utilize HDMI... so unless you have at least 3 HDMI ports, you'll want an HDMI switch for this. You can find a manual-select 3-port HDMI switch in most department & electronic stores (like Walmart & Best Buy), but you may be able to find different size switches (2-port, 4-port, ect.) & features (auto-select, ect.) online. Any reputable electronics associate should be able to direct you to them (assuming they're in stock).
The Wii will want to use a composite (3-port) connection, unless you opted to go with the component (5-port) cable... which shouldn't be an issue as you're using a different set of ports instead of HDMI.
While HDMI splitters or Y-cables do exist, they can only split the signal out from a port & cannot merge two signals into a single port. This is mostly due to HDCP (HDMI's DRM measures) & HDMI-CEC (which allows a connected device to control your TV to some extent... like turning your on & selecting the desired input for the device that sent the CEC request, like a BluRay player OR a game console). HDMI splitters can also degrade A/V quality (as half of the original signal is go to each device on the receiving end), so things may not look or sound as well as it could. This is WHY a HDMI Switch is utilized to allow multiple devices to connect to a single port, as only one device will be actively connected at any given time.
Hope this helps!