I dont know DD if you like Datsuns lightweight simple design then....
1. DCT rwd BMW box is around 60-75kg all up
2. you also must welcome headaches from phantom issues ready to pop up from being a beginner at setting it all up with sensors all over the place.
3. Datsun folk like mechanically simple devices usually with less ecus the better for overall reliability.

In my case I really like this full mech setup that can be taken out with 4 bolts
much like the t5's bellhousing, front input shaft bearing holder/cover and shifter.

That shifter mod doesn't convert the T5 to DCT. It's still a single clutch with main and cluster shafts. And I'd be worried more about the dog teeth getting busted than the syncros needing regular replacement with its rapid gear changing.

No one said anything about a shifter turning a t5 into a DCT thats crazy talk.
Its a v8 box that weighs the same as an old stumpy L6 R30 but takes v8 torque.
No A15 will outlive it seq or not, its the fave car club box worldwide for solid reasons.
They are abused probably mostly by Irish Ford Escort rallye drivers behind crazy hp
even behind 650hp sierra turbo beasts and many fox bodied turbo mustangs to name a smidgen.

Sequential shifter would be great for the many who don't know how to drive a stick shift

Actually it would be worse if they couldnt in the fist place
its really a novelty item or where every micro second counts