NeophyteOk, i'm getting a better picture of your problem (not clear but getting there). You need the threshold to apply to some instances but not others. And that means setting the threshold manually on each instance, which is not scalable.
The traditional way of handling this is to split the datasource into two copies: one for the instances with one threshold and one for instances with the other. You limit the discovery of each datasource to include only the instances in that group (discovery filters are easiest). That way you have one datasource that is doing what it's doing now, except not monitoring the instances that need the different threshold. The new datasource is only monitoring the instances that need the new threshold. This lets you set the threshold globally, but have it only apply to certain objects.
Is there a way to programmatically (i.e. querying the device during discovery) determine which ones need the other threshold?
