Multiple VPNs with one fixed external IP

From the looks of things, you will need to make changes to both VPNs.

On the Home <--> Work VPN, you will need to make sure that all your remote networks are routeable from your home worker VPN clients.

There are two options for this:

1. Send specific routes for all of your remote networks as part of the VPN client configuration. This could be quite configuration intensive if your client/remote server VPNs are spread across lots of different address blocks.

2. Configure your home worker VPN clients to use their tunnel interface as their default route. This is a lot simpler from a configuration management point of view, but it will force all traffic from the VPN clients through the office, including their browsing traffic, which may not be desirable.

Could you be a little more specific when you say your home users use hardware VPNs? Do you provide a VPN appliance that they plug into their home broadband, and then plug their laptops in behind the VPN end point? If that's the case, then the above probably won't be needed, as the home VPN client's default route will point back to the office.

On the Work <--> Remote Server|Client Site VPNs, you will need to advertise routes for all of your 'Home VPN' address ranges. (from your example above, 192.168.1.0/24). How do you currently exchange routes with your clients and remote service sites?

No. Not if the VPN client makes itself the default route for all traffic and defends its position by stopping you setting up alternative routing after successful connection (which it probably does).

On the off-chance that it doesn't defend its position as the only route for network traffic you can try editing the routing table yourself, but I'm not all that familiar with this under Windows (I'm more a Linux man in that area) but perhaps someone else might be able to help. If you can reset the routing table such that the machine running the VPN client can see, and respond to, your local LAN you can then try configure ICS, or some other form of NAT, to "share" the connection.

This might be a case where you have no choice but to simply explain to that client the if they don't give a little regarding the VPN access, you will have to lengthen any project time estimates to account for not being able to have two+ people work concurrently on the project at times which it would be a great help, or you will have to charge extra to cover overtime if developers have to work late to finish project work because they were waiting for the VPN connection to become free earlier. Of course if they are a significant client and you have direct competitors they might consider using this could be a dangerous position to take, but that is a business decision rather than a technical one.