How can I configure a profile to use the linear tone curve that is associated with a raw file?

code behaviour (based on Process version used for example) and/or content of all profiles used... again - if you have to use ACR and have to be sure - use simple matrix DCP camera profile alone with explicitly embedded linear curve and proper process version... if you are using process v2012 you can't get linear behaviour around clipping (and even not around it),  so forget it... C1 for example has a special flag in .fcrv files (curves data) that will switch on/off special handling around clipping... but if you are fine with non linearity from the code then simply embed linear curves in your profiles explicitly

For what you're trying to accomplish (normal image processing) there is no need for "specialized" processing.  The PV2012 controls apply some highlight recovery and set the Black Point with all of the Basic panel controls set to 0. In a normal workflow select the camera profile (Adobe Standard, Camera Standard, Camera Neutral, etc.) that provides the most pleasing rendering BEFORE making any other adjustments. Even though the controls are affected by the tone curve in the camera profile no actual raw data is lost. It can be recovered using the Basic panel Tone controls as I've outlined in the tutorial at the below Dropbox link. I hope you find it helpful and please let me know if you have any other questions.
https://www.dropbox.com/s/lsl4jfswwoc1yo4/Lightroom%20PV2012%20Basic%20Tone%20Control%20Adjustments.pdf?dl=0

Todd,
Thanks for the link. An informative article. As for Adobe baked profiles; I rarely use them. My default has been to create camera specific profiles using DNG Profile Editor for each of my cameras.
The reason for wanting to have an option to have a true linear tone curve is so I have an optional starting point for a file where I want to pay particular attention to highlight detail and/or shadow detail.
All I'm trying to get to is a known starting point rather than an unknown starting point.
Not sure why Adobe isn't more forthcoming with that as an option.
Its really frustrating when processing an image to know that there is fine detail in highlight regions and see them disappear as I get the brightness where I want it. Same for shadow detail. Especially when working to get the middle of the tone curve to a slope for pleasing mid-tones.

I guess bottomline is that I want to use Lightroom to apply a characteristic curve that I control rather than one with hidden tweaks that I have to find a way to neutralize.
I spent a lot of time, with film, fine tuning developing techniques, along with exposure compensation and selecting film emulsions in an attempt to control the tone curve to maximize response to the scene tonal range. Then selecting paper, developer along with dodging and burning to get the print I wanted.
I'd like the same capabilities with Lightroom and Photoshop.
Makes no sense to me for Lightroom engineers to tweak a linear tone curve and still call it linear.

The best suggestion I can offer is to change your Default Develop Settings for Highlights from 0 to -50 and Shadows from 0 to +50. You may find a lower setting works better like -25 and +25, but I suggest keeping them opposite and equal.

You'll need to change the settings for each camera model with a raw file selected. Hit the Reset button at the bottom of the Develop controls panel. Next select the desired camera profile, adjust Highlights and Shadows as suggested. Then hold down the ALT key and click on the Reset button again and click on 'Update to Current Settings.'

Todd,
That's what I've been doing for years.What I'm looking for now, since Adobe has added the Profile module is a way to build profiles that can be easily applied while importing the files into Lightroom with the sliders then able to optimally fine tune the file.

Here are three screen captures of a file to illustrate how Lightroom impacts the file differently based on the underlying tone curve and camera profile.

All settings were left at Zero or the same value except for the highlight, shadow, white and black point. All three files have the same tone curve applied. Its the Adobe steep curve with + and - 15 added. Here is the tone curve as applied. 

This one is with the profile set to Adobe color;


This one is with the profile set to the profile I created for GFX using DNG Profile editor and the standard Adobe tone curve. The profile was placed into the profile module by Lightroom when it updated to the latest version.

This one is with the profile set to the profile I created for GFX using DNG Profile editor and the linear curve option. I then created a profile following the process described in the SDK PDF file. The 4 at the end means its using the Version 4 processing.I made adjustments using exposure and highlight/shadow sliders to adapt a Macbeth color chart gray scale during the process. I used the same Macbeth image file with Version 2 processing applied as the basis for the adjustments.


It may be hard to see without having the files at full size, but the detail in the bright area and clouds are much more detailed and subtle in this last example.
I think I've got a useful camera profile for the GFX-50s but without any empirical data about whats going on. And its a pain to have to go through this process for every camera.

So you want to create dcp camera profiles with a linear tone curve and then use the new XMP profile tools to piggyback custom Tone controls and Tone Curve settings correct? Sounds like a good idea to me, but I haven't worked with the new profile creation tools yet in ACR 10.3. Someone else landing here may be able to help. I suggest also posting your question in the Camera Raw forum. It may get more attention there: https://forums.adobe.com/community/cameraraw

One "piggyback" concern I would like to point out is that all of the Develop controls have limits. For example if you apply global Tone panel  -50 Highlights and then use the local Adjustment Brush to add more -Highlights the maximum effect will be Global + Local = -100. I'm fairly certain this same limit applies to when using the new XMP camera profiles. The sum of all three control settings (XMP Profile, Global, Local) will have an effective limit of the control's min and max settings (i.e. Highlights ±100).

UPDATE: I just tested the above described limit by creating a new XMP camera profile in ACR 10.3 containing -100 Highlights and +100 Shadows. When the camera profile is applied to an image file the Basic panel -Highlights setting has no effect and the same for a +Shadows setting (i.e. at max 100 limit). This confirms what I stated above and should be taken into consideration when processing image files so you don't get unexpected results.

>  I prefer the parametric approach

all raw converters are parametric ...

They are until the settings are baked into an output file.
I want to go from Lightroom to Photoshop so that I can use smart object capabilities to continue to refine the parametric settings.
Working with TIFFs from a raw converter means that Photoshop is starting with baked in processing from the raw converter.