PC to Mac Remote Management

We ran into the same problems because of mobile devices. Any device hardwired was easy as it's IP never changed and VNC works for them. Best fix was to setup ESXi server and make VM's for each tech. Let them customize it and break it, learn it, etc. Then they can use Screen Sharing or Casper Remote from within the VM. This also allowed them to use their VM from anywhere, not just their desktops. We did need set some settings.

Our first boot script handles this for us.
1. Make sure VNC password is enabled
2. ARD users and privileges are set.

#Set VNC console default here
defaults write /Library/Preferences/com.apple.RemoteManagement VNCAlwaysStartOnConsole -bool true

# Reset VNC Password
/System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -configure -clientopts -setvncpw -vncpw PASSWORD -restart -agent

# Reset Screen Sharing password and privs
# Set ARD privs and users with these two lines. They MUST be separate lines!
/System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -activate -configure -allowAccessFor -specifiedUsers
/System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -configure -users USERS -access -on -privs -all -restart -agent

There are many cross-platform remote assistance tools available. You may already have access to one.
Most chat clients and remote meeting software has some sort of screen sharing capability.

Bomgar - https://www.bomgar.com
WebEx Support Center - https://www.webex.com/products/remote-support.html
Cisco Jabber - http://www.cisco.com/c/en/us/products/unified-communications/jabber-mac/index.html
Citrix Go To Assist - https://get.gotoassist.com
Lync Desktop Sharing (Skype for Business for Mac does not fully support this yet) - https://support.office.com/en-us/article/Share-your-desktop-Lync-for-Mac-1FD36E20-424F-41E5-8669-B459248C6F4A

Thank you @millersc and @ericbenfer . I'm going to look into these suggestions.

There is also Remotix which allows Windows users to connect using Apple's native Screen Sharing protocol. See https://nulana.com/remotix-windows/. I have not personally used the Windows version so I can't speak to how well it works, but I have used the iOS version at home and it has worked really well to connect to my iMac.

you could also use teamviewer

Different VNC clients will work with macOS' VNC server, assuming the Mac side is enabled (note that a password must be set on the Mac VNC server to accept an incoming connection), it's a matter of figuring out which settings work on the Windows VNC client side to successfully connect - this varies by Windows clients and not all Windows VNC clients can successfully connect to the native Apple VNC server. Unfortunately no Windows VNC clients natively support the Mac VNC functionality of ARD that tunnels authentication through SSH and supports drag and drop file transfers.

There are a few different paths to take here:

1. Field engineers leverage SSH to remote into the target Mac and activate VNC/ARD with the kickstart command. Initially this will have a modest learning curve but it is very reliable and reproduceable.
2. Acquire one of the other licensed remote control services mentioned above.
3. Roll your own Self Service "Remote Desktop Support" button which, when a user is directed to use this by a field engineer, collects the relevant information (ip, trouble ticket, et cetera) and feeds a well constructed VNC connection file to the field engineer leveraging JSS backend automation and the APIs.

TeamViewer.

Thanks everyone. I am looking into these solutions.

You can use on premise R-HUB remote support servers http://www.rhubcom.com/v5/remote-Support.html for remotely accessing MAC computers from PC. It provides simple and easy to use interface and works from behind the firewall, hence better security.