The asset discovery module is still maintained, not sure what you mean here.
The auto-discovery module, on another hand, is kind of deprecated because the new mechanism of relays selection we have introduced for several years are supposed to be much more efficient.
I'm sure you already know it, but it is actually possible to deploy a new dhcp option by script, but it depends of the level of access you have at your customers sites, e.G How to set DHCP scope lease time through netsh? – Ananth Anto's Blog.
I think that the relay list cannot be set up in your environment, because I suspect a lot of your customers have the same ip range, if not it could be a solution.
If you have access to the dns server on site, you could set a dns alias and have all the devices configured to use this dns alias as the parent name. This way you could either use a regular parent name without the hassle of setting a dhcp option. We have several customers who proceed this way.
Do not hesitate to open a case and we will discuss your options by phone, it'll be easier with the exact context.
Thank you Julien,
I will created idea on this module to add ip scan with local ip and not the wan ip.