How can I provide easy transparent access to internal resources from a web browser

My company has a field engineering force which works onsite at customers. Many of those customers have very restrictive rules. One cannot usually connect a non-customer owned laptop to the network, our employees can't install non-approved software on customer workstations. The customer network frequently has restrictive firewall rules in place that prevent access to external resources. Even our webmail is often blocked.

Meanwhile, we have a large number of useful resources on our internal network. Lots of wikis and similar resources, mostly browser based.

One idea I was thinking of is a browser based VNC that can talk to the my company's web server via http/https. In this way we should be able to access it from a customer machine using a customer web browser over ports that the customer would have open in the firewall. The web server would then forward the VNC connections to a generic Linux box. The Linux box would provide a web browser, rdesktop, and other apps and would be sitting within my company's network, with access to all the internal resources.

My questions are as follows...

1) Is this a good idea, or is there a better solution?

2) What products are available to do this?

3) Are there combinations that are known to work?

Thanks.