There are a couple of improvements that can be made performing an import scan.
1. When detecting HTTP port being open, check the response code. If its a redirect, e.g. 302, then follow the link. This will often be the real website. Often it would be the https equivalent, other times it may redirect you to another port 5000 (e.g. Synology), or sometimes its the DNS equivalent (e.g. 172.16.11.11 may redirect to app2.example.com).
2. When you detect https, if the page contains "vSphere Web Client" then the host is a vCenter host and you can create respective entries for it. For example, you could ask for a username/password which then imports all the VMs and organize them in a similar organization than they are in vCenter.
3. When you detect https, if the page contains "ESXi" its a vSphere host. You could create the respective sessions used for vSphere.
4. When you detect http or https. If the page contains "DSM Help" this is likely a Synology DSM host. You may want to check if port 5000 or 5001 is open since this is the default ports used by Synology DSM.
5. When you detect http and https. If the response "Server" headers contain "Procurve Web Server" then its an HP Procurve device.
6. When you detect http and https. If the page contains both "Welcome to Server" and "Apple Inc" then its an OS X server.
In essence, there are hundreds of ways to detect the host. You can find such signatures in penetration software etc. You can use this information to populate the inventory in RDM.