You configuration will definitely work it is just a matter of how well it will work. With the addition of multiple patch cables and wall runs, you want to make sure the total cable length from the switch to the host is well under 100m. Depending on the switch, you probably want to make sure the wiring through to the client is all "straight through" and not cross over. This will help in troubleshooting layer 1 issues, but if the switch is newer then it probably have auto-MDIX that will auto detect the receive and send pins and switch them accordingly.
My other concern is the exposed patch cable between A1 and B1. If this is in a public area then it may be better to put that behind the wall plate to reduce the chance of tampering. Also If I were to see a wall jack plugged into another wall jack, I would immediately think a switch loop was present because normally all of the horizontal wiring runs back to a switch.
Other than the above considerations it should work.
Josh
You'll find that the ethernet sockets you're speaking of are actually a switch, on those smaller routers.
Cisco does the same thing with SOHO-type equipment, eg 867VAE, for the same reason.
[EDIT rewrote from here down]
With a 2811 you can add a switch module in just the same way, such as HWIC-4ESW. Switch ethernet ports are also called Layer 2 ports, and they are associated to a VLAN (by default VLAN 1) and can be set to be trunk ports, access ports and so on. These are expected to be faster for switch-like behaviour.
You can also add more "layer 3" interfaces, such as with HWIC-2FE. These have IP addresses, access lists and so on. These are expected to be faster for routing behaviour.
Somewhat confusingly, both types of interface are written the same way,but if you, for example, put an IP address on an L2 interface you get an error:
gw(config)#int fastEthernet 0
gw(config-if)#ip address 1.2.3.4 255.255.255.0
% IP addresses may not be configured on L2 links.
If you have a need for say, four interfaces with 192.168.0.1/24 through 192.168.3.1/24 on them, with routing and access control lists, NAT, etc, then there are a couple of common approaches.
Use lots of L3 interfaces in the obvious way
interface fastethernet 0/1
ip address 192.168.0.1 255.255.255.0
interface fastethernet 1/1
ip address 192.168.1.1 255.255.255.0
...
Use switch ports, with lots of VLANs [EDIT: corrected this to a config which is correct, from an 867VAE with 15.2]
interface FastEthernet0
switchport access vlan 100
no ip address
interface FastEthernet1
switchport access vlan 101
no ip address
...
interface Vlan100
ip address 192.168.0.1 255.255.255.0
interface Vlan101
ip address 192.168.1.1 255.255.255.0
...
Quite how you make VLANs varies on different routers. On a 2811 with the built-in interfaces (tested on 15.1) you can use an external switch with VLANS, and use "subinterfaces" which look like this
interface FastEthernet0/0
no ip address
!
interface FastEthernet0/0.100
encapsulation dot1Q 100
ip address 192.168.0.1 255.255.255.0
!
interface FastEthernet0/0.101
encapsulation dot1Q 101
ip address 192.168.1.1 255.255.255.0
...
Choosing between these approaches depends on the hardware you've got. There are sometimes performance complexities or subtle restrictions eg max ether HWICs for a chassis. My understanding is that some Cisco L3-capable interfaces can be put into L2 mode, and they enter this by the switchport command; but some require "subinterfaces", see below.
A structure which is extremely common is sometimes called "router on a stick". A router is configured with one L3 towards internet, and one set as a trunk port towards a switch. The switch has many VLANs; the router has many interface vlan lines.
Note also the so-called "Layer 3 Switch", which is a switch with a router in it that can be enabled in configuration. The difference between a router with a switch in it and a switch with a router in it is mostly one of engineering emphasis; for many purposes it's just a question of which has got the interfaces you want, and perhaps the routing protocols and higher level functions.
Best Answer
To expand on @Zac67 's comment, you will need to purchase a router to direct traffic to each modem, as well as be a single source for DHCP. This may require reorganizing your network switches, depending on where the physical connections are located.
I should point out that it is difficult to distribute traffic across both modems. Generally one ISP connection will be used, and the other will serve as a backup connection in case the first one fails.