In my lab I connect every interface of the firewalls and routers to the layer three switch. I make a spreadsheet that lists all the ports of the switch and then identifies which device and interface is connected to each port.
I then create the 3 (or maximum available) routing instances on each firewall and distribute the interfaces among them.
Create a virtual internet
I assign a private range for my virtual internet. Then carve this up into a series of /29 addresses. This is another tab in the spreadsheet.
Now I assign every device in the lab a "wan" public address for their use.
On each interface that will be a "wan" on the virtual routing intance or physical device I setup the default gateway for their wan segment as an RVI.
Now all the devices can create vpn or other "internet" connections across my private internet.
Setup base config
Now configure the wan port and default routes in each routing instance and device for this topology and confirm access to each other.
I save these configs out for easy reset to base.
Console access
If you can get a console server you set that up with every device so you can use the console port over ip.
Otherwise put an old pc next to the stack with a com port cable you can move around as needed. Then rdp into that pc to do the console access.
Daily use
With this arrangement all "cabling" changes then are simply a configuration change on the switch. You create and change vlans to be in the same one if you need a connection.
For example: to connect the routera port 1 to firewall b port 1 you just configure their connected switch port to be in the same layer 2 vlan by themselves. They are connected.