I won't lie, parts availability is a concern. But HPI seems to be continuing to rebuild their brand (albeit very slowly and with more than one stumble in the last few years) so I'm still optimistic the situation will improve but there's definitely no guarantee.
My Venture is hands down, without question my favourite rig in my fleet. Out of my 10.2 (it's been sold now), my Bom or anything else is or ever has been in my stable, the Venture gets more wheel time without question.
This might seem excessive to some but I actually bought an extra SBK to keep around for parts, realistically the cost of an SBK is really good value as compared to buying trans gears, t-case gears, axle gears, axle housings, trans cases, etc, etc, etc. But in over 3 years (I got my first Venture on release day) I've used/needed exactly zero parts from that kit, I've actually sold a few things (namely axle tubes, cvd's and alum links) from it to recoup some funds.
I did break an HPI CVD once but that was a stupid mistake that led to a massive cliff fall. Regardless, I recommend upgrading to the RC4WD universals anyways. They're stronger and turn a bit better.
If you upgrade to aluminum hubs & knuckles the Venture is an impressively durable rig. The trans and t-case are well designed/built, the diff gears seems to mesh really nicely and the axles shafts have never given me any issues. I don't drive gently (Homes brushless/3S/35kg servo) and the only parts I've actually broken on my Venture are rod ends which are pretty much universally replaceable.
There is minimal aftermarket support for Venture, but beyond hubs/Knuckles forward battery mount and metal links I don't see that much is required.
(If you buy one, pm me and I'll hook you with files to print a good battery tray)
I feel like my post has been a bit rambling but to briefly summarize - RC4WD Universals are good, aluminum hubs/knuckles are available and I don't think there's any other proprietary parts that are required to upgrade (I'm not mentioning metal links because imo those are effectively universal).