Yes. sys admins of the clients would have to set up their machines individually to trust your assembly (or domain). about the network size, the apps will only get downloaded if:
1) the file the client has is outdated. (there's a new version out)
2) the client does not have the file.
and the the client only accesses the server when first loading the assembly. once the file is downloaded, it's kept in cache. so theoretically, your client could even run the app if your server is offline or the client is offline
if you want to know more about this, Google for "Smart Clients". there's plenty of information out there.