Let's back up a second before considering the architecture. Your ISP offers 100Mbps, but your wireless router is limited to 54Mbps, and you have a lot of users on the one wireless router, all competing for that shared wireless signal. Definitely not a good situation.
So I understand why adding a second wireless AP would increase your local wireless throughput. What I don't understand is how having a second public IP provides any additional benefit?
Not unless you're assuming that EACH public IP is getting 100Mbps, which I seriously doubt. Your ISP is more than happy to hand out multiple public IPs for a price, entire BLOCKS if you need them, but that doesn't necessarily mean he's adding bandwidth PER public IP. Not unless you actually confirmed that w/ the ISP.
The most common reason ppl need multiple public IPs is so they can establish a unique presence for the various services they're offering behind their NAT router, rather than port forwarding everything from one public IP. It normally has NOTHING to do w/ bandwidth.
So before even considering the architecture, what’s the goal here? What’s the problem you’re trying to solve? I sort of get the part about the wireless bottleneck, but the multiple public IPs I’m not so sure about.
My idea/question is to connect a second w/router with a different SSID to have half of the users connected to one router and half to the other. this way I can take advantage of most of the bandwidth from my ISP. My question is if the modem (which has only one WAN port) will recognize both routers (using a switch to connect them)?
or will it better to have a couple of AP around the room connected to that g router?
If I install 2 extra AP... will the router be able to handle, let say, 30Mbps from its own plus 30Mbps from each AP?
As you can see, I'm just trying to find the way to take most advantage of the 100Mbps from the ISP having only 54Mbps routers/APs.
Ok, I get it. But using multiple public IPs as you've described the situation seems irrelevant. As long as your existing wireless router is able to support 100Mbps over its WAN port, that’s all you need. The only possible concern I would have is that since you never get 100% efficiency w/ ethernet, it would be better if the WAN supported gigabit speeds (1000Mbps). But most consumer routers are only 100Mbps over the WAN. A 100Mbps WAN might only get you say 85-90Mbps actual. But for now that’s a minor quibble.
Since you're only trying to increase the *local* wireless throughput, you just need additional APs. Of course, they need to be using different freq/channels (for G, preferably channels 1, 6, and 11). They can either be dedicated standalone APs, or even cheap wireless routers reconfigured as APs (give them a unique static IP and disable their DHCP servers). Just patch them to the router LAN to LAN. No matter how you distribute the wireless access between them, all the router needs to handle is 100Mbps since that’s all the ISP is delivering, and which is far below your router’s maximum capacity (your typical consumer router has 4 x 100Mbps switched ports, so we already know is can handle up to 400Mbps across its switch).
So unless there’s something more complicated here that I’m missing, I’m just not seeing the need to involve multiple IPs and WANs. That gets you into all kinds of other messy problems (e.g., users being on different local networks). You want to avoid that as much as possible.