Ah, I think I see now Glen with the extra info you've supplied.
I know when I ran my 2m & 70cm double-extended-zepps to the loft not only did I have to use a duplexer to implement one coax feed I also had to keep the antennas away from each other as well as from the HF fan-array. Luckily the loft space is big enough that I could get such separation.
The willing 'volunteer' that assisted me to install them did hang them too close to my fan array feed to start with and I had interaction problems so they were moved further away from each other. It's quite the mess up there now but finally all worked.
Thankfully the gracious donation to me of a NanoVNA helped a huge amount in resolving those difficulties but I still had to feed a further line to my VHF Horizontal Halo and luckily that antenna was in the clear.
All my coax lines run together from the shack to the loft but the use of common-mode choking has helped there too.
From there the HF array is fed from the bottom with the coax running vertically down but the VHF/UHF vertical dipoles have the feedline presented to them horizontally and the Halo also runs away from it horizontally as it is mounted in the clear.
Can be quite the challenge to muster the ability to have decent multi-band antenna systems!
Our own fault for being so greedy with band usage.
(I now have everything albeit not perfect from 160m through to 70cm - God help me if I get interested in 4 or 6m too!)
This is all going to be a problem if running everything off one mast, I can see each antenna interacting with each other especially the T2LT or coaxial shrouded dipole if the top section isn't in the clear. The coax feeds for that and the dipole for 17m will obviously interact with the 20m vertical too if that is running up the mast.
Bit of a nightmare scenario you've got there Glen!
I'm not sure off hand if this can all be resolved but I do understand why people run Cobwebbs & Hex-beams for multi-band activity being smaller footprint versions of a fan-array. It's all about impedances and proximity interaction.
I'll think on this some more and hopefully someone else may be able to provide some insight also but I think it's a difficult one.
All the best,