Interneg film - now discontinued - was a low contrast panchromatic film. I have read of unsharp masking in Photo Techniques magazine Howard Bond (2006-2008 I think) using TMAX 100 where panchromatic masks were required. It is possible to do this striaght to 8x10, but it is an expensive way to go.

I would suggest that you make an interneg using a pan b&w film; tmax is exceptionally fine grained and would work well. Calibrate your process. You need to make tests to figure out your real film speed, to get (in you case) the slide shadows off of the toe of the tmax film. Then you want to develop to expose properly and develop to a moderate contrast, to stay in a linear portion of the interngative HD curve.

You may need to pre, or post flash the interneg film to reduce contrast. This is most easily achieved in a slide duper, like a Bowens Illumitran, staying with 35mm.

Once you have the now b&w interneg, than you can work with orthochromatic 8x10 (cheaper than pan film and easier to work with, under appropriate safelight), or larger, film to make the large postive, then contact it for the chrome contact neg.
There are other options, such as reversal at the 35mm interneg stage, or reversal once you go to the full size contact sheet.

Here lith film is just the thing. Something like Freestyle APS I think. I have a freezer stash of some old graphic arts stuff, so I have not been looking lately. It can be developed in Dektol, or D-76 , or weak dilutions of hc110 etc to get continuous tone results from Lith film.

Your best friend though this process will be a step wedge. It will let you see what the contrast range and scale expansion/contraction you are dealing with, at each stage.