My travel rig:
Alloy BP with Hog harness and weight pockets (cam bands and waist harness - up to 18#)
Apeks XTX100 DIN regs with miflex hoses including 5' primary, & SPG
30# singles wing
Size L Jet Fins with neoprene socks (I usually use XL Jets with booties)
Halcyon oral-inflate SMB
75' spool
3mm shorty wetsuit
2.5mm hooded vest
1mm Nylon undersuit (if it's cold)
Frameless mask
Wrist-mount dive computer
1mm tropical gloves (if it's really cold)
Save-a-dive kit of spares and basic tools
Log book and required c-cards
I find this combo adapts to most conditions I dive in without taking up too much space/weight. It all fits comfortably in a small Tatonka gear bag, total weight <14kg. Can fit in a papaerback and a spare t-shirt too.
I use hard weights and a single DIN tank supplied on site (I'll pack a yoke fitting if required). If need be I rent a thicker wetsuit, the BP and weight pockets work for up to 7mm for me, which is good for ~19C and I don't like diving anything colder than that anyway
I'm still thinking about getting some Apeks Flight regs though to lighten it a little. I tried some XL OMS Slipstream fins instead of the Jets but while they save weight they take up more room and I didn't think the tradeoff was worthwhile
If I'm travelling really light - work trips with some diving on the side - I just take a mask, computer or Aqualand watch & swimming trunks, and rent the rest - but I miss my BPW & fins