I'll have what Per's having!
This is a tough one, I've been thinking about it but held off answering - so much to consider. Like the length...
A shorter blank?
I've been playing with a 12'6" 9wt sage euro and 8/9 midspey and it's a lot of fun - in fact it might make a nice alternate to my 7136-4 for small river work but it feels a little short on the kick (keeping the d-loop up) and mending. No, too specialized - nothing too short could be "ideal" for the range of rivers I fish...
A longer blank?
For the longer lines like the Rio Grand Spey and XLT, I'd like the 16' (17,18...). On big rivers such rod/line combinations are the ticket but personally I couldn't say it would be perfect all-around because of the smaller rivers I also love to fish.
So I guess the length would be 14 or 15 feet, 14.5 might work.
Number of pieces - since I've had to move away from steelhead country, I now have to travel to get back there each year. Three pc 15 footers are cumbersome - I would like to have a 6-pc Spey rod that would break down to 29 (14.5 ft) inches or 30 inches (15 ft) and fit in my suitcase. Heck I would tape the ferrules anyway, and to break down I could fit into any sedan with the middle ferrule untaped and broken down.
Guides - The Sages, T&T's etc all use the best guides so my only wish would be that the upper guides be a little bigger so I can squeeze a folded extended belly line through them at the river. I like the silicon carbide or other high-grade ceramic tiptop because of the increased friction at that point on the line, especially for over-hang running lines like heads.
Line weight - for me the best all-around is 9wt, I've fished a wide range of summer and winter situations successfully with 9wt gear. Might not get the distance of the 10/11 rigs but it casts well enough and certainly catches fish. I would love to greaseline a 7wt all day long but winter is inevitable and has it's own charm.
A perfect rod would (knowing a lot of this is the line match):
(a) pick up and set most if not all of an extended belly (Grand Spey, XLT, etc) easily, also work a mid-length head like poetry in motion and cast a compact deep-winter head easily too (same rod)
(b) kick a sharp and energized d-loop without drooping, and communicate what's going on back there before firing
(c) have the modulus/recoil to put a wind-biting wedge into the line yet...
(d) sweet in the heart of the blank so you can spring-load finesse casts without working out when you don't need to reach the other bank
(e) I like the full cork lower ball-end handle like the one on my old IMX 15'ftr maybe a little more flange to it
(f) I'd like the natural grip points on the handle to be at the optimal location. Some of my grips are easier to hold where the rod performs less optimally (hand gravitates to these off-positions)
(g) aesthetics top notch of course
(h) warranty unconditional with exceptional service (ship to lodge, etc)
(i) durable, not prone to explosion even when snake rolling a long heavy belly with a sinktip
... and never come loose at the ferrules unless I loosen them!
Someone recently mentioned exchangeable sections to change the line rating of the rod, that was pretty interesting. I think the rod was a Daiwa Amorphus Whisker (?).
Dana, you made me realize something with this question - how glad I am to be able to have a summer rod, winter rod, and something in-between (big summer, light winter). I would be able to narrow down each of these much easier than to combine the niches into one.
.02
Juro