Avid Pro Audio Community - Thunderbolt 3 chassi for HD TDM?

Pro Tools 10.3.10 worked fine on Windows 10 with HD TDM, I had my own system running for a few years in a HP Z800 on Windows 10 Pro.
With regards to Thunderbolt and the chassis with HD TDM cards, Thunderbolt in operation is just an extension of the PCIe bus so what works for HDX should very well work with HD TDM cards. I have a sonnet Echo Express 3 (thunderbolt 2 with an apple TB3 to TB2 adapter) running just fine on my current Windows 10 system but not with HDX or HD TDM cards (with a blackmagic video card and UAD Octo).
So the chassis I say no problem and the cards theoretically no problem.

HOWEVER:

I wouldn't recommend anyone to go down the path of HD TDM these days unless you are really interested in head scratching and disappointment and enjoy a challenge.

Someone asked a similar question in out Pro Tools Windows User Group facebook group recently and here's my answer edited to suit answering you here too, it may be more info than you are asking for but its all in context of the subject:

I've built windows TDM systems dating back 20 years and to be perfectly honest if you are dead set on continuing to use TDM dsp cards you will be better to stick with computer hardware of a similar generation, the old TDM architecture doesn't really share well with native so a faster/newerU isnt going to be as great as you may imagine.

It's quite understandable for people to think that they could boost the horsepower of their ageing TDM system by adding more native cpu power but that's a problem in itself.
The TDM systems and still HDX to a certain extent were designed with the dsp cards taking all the processing load away from the native cpu so the dsp audio engine is best left to have total control and governance of Pro Tools.
When you want to try and use both TDM DSP and native processing together the transport routes the DSP uses to get from DSP chip to native CPU and back again use a lot of resources (voices) and PCIe bus bandwidth and also induce latency during the round trip.

So with DSP systems you should always be using DSP first and foremost and at least always first in any plugin insert slots in the mixer.
You can stack native plugins afterwards but as I said latency due to the routing will become a big factor and ultimately this leads to frustration and instability and most people just give up because of this.

So with that said I personally wouldn't bother these days.
an HD TDM system still has a perfectly valid place as a low latency tracking rig but for a versatile powerful mix rig I would build a native system with PT2020.

You'll save yourself a lot of headaches and potentially money too.

I did build HD TDM PT10 systems on newer Pro Tools PC designs before discontinuing them because the amount of R&D sourcing and testing boards and the trade off was no longer viable. Not just any board and no "one" manufacturer is an answer trust my experience on that one you have to try many many boards to find the right one.

resource sharing and conflicts are a mind bending juggling match to get something usable and stable.