Which area should I compromise?

Full questionnaire here:

Spoiler

General Questions.

1. What is your budget?
£2-3k (GBP)

2. Would you consider purchasing used/refurbished?
No

3. Do you prefer a media/mobile tablet like the iPad, Windows tablet PC, or notebook convertible?
Convertible Windows device to replace both aging Windows ultrabook and Android tablet - preferred form factor is detachable, such as Surface Book or a tablet with optional keyboard, such as the Surface Pro

4. What size Tablet PC would you prefer?
12-14"

5. Which country do you intent to purchase from [where do you live]?
UK but would purchase from EU if that works out cheaper

6. Do you have any preferences to brand loyalty or dislikes?
Like Samsung, ambivalent towards HP but am willing to consider any/all options on their own merit

7. How many hours battery life do you require?
The longer the better, as will be travelling frequently with work

8. What will be the primary usage scenario of this tablet? (Email/Web Surfing/Drawing/Word Processing/Entertainment/Notetaking etc)
All-round device - MS Office, some light PS/GIMP and maybe CAD, light gaming, multimedia etc

9. Do you have an OS preference? For example, do you own an iPhone and a Mac, or are you a Windows fan? Do you own an Android device and use Google services frequently?
Windows - neither iOS or Android will cut it from a productivity point of view

10. What software and tasks do you intend to run? (Microsoft Office or other Word Processing Suite/Photoshop/3D Studio Max/Autocad etc)
MS Office, GIMP, AutoCAD occasionally, some gaming but older titles

11. Do you intend on playing Games? If so please list.
Yes but nothing intensive - older RTS titles such as Red Alert

12. Would you like to stream content through your home theater system?
Maybe occasionally but not a primary concern

Screen Specifics

1. Any preference on screen resolution?
QHD or better - current Ultrabook is 3200x1800 and would prefer something not too far off that

2. Will you be using the tablet outdoors? Do you need to be able to see it through glare from the sun?
Sometimes but again not a primary factor

3. Do you require a pen? With or without pressure sensitivity? Do you prefer Wacom EMR, AES or N-trig?
Absolutely
I'm used to Wacom EMR pens due to multiple Samsung Notes and always liked them but any decent pen input system will do

Component Specifics

1. What size Hard Drive and Memory do you require? Would you like expandable memory?
512GB SSD, 8GB+ RAM

2. What sort of inputs do you require, if any? Would you like full-sized USB and SD card slots? Are microUSB and microSD ok? Do you require HDMI inputs?
No specific needs

Misc
1. Other non specific items ~ please add other items you require not covered above?
LTE connectivity is high on the wish-list

2. Additional requests ~ anything other you wish to take into consideration?

TL;DR version - looking for a Windows detachable tablet/2-in-1 with:

• Decent all-round specs (~i5, 8GB+ RAM)
• 512GB+ SSD
• QHD or higher screen
• Good pen input
• LTE connectivity
• Decent battery life (10 hours+?)

However, after much looking around, I don't think I can find anything that ticks all the boxes - with one possible, long-shot exception. So I'm looking for some advice/suggestions, either to help me decide which area to compromise on or to suggest an option I may not be aware of.

The contenders are:

Microsoft Surface Pro (LTE)
Pros & Cons:

Spoiler

Pros:

• LTE connectivity
• Good battery life
• Fanless
• Decent pen

Cons:

• Maxes out at 256GB storage (thanks MS...)
• Not currently available
• Not 100% convinced about the keyboard covers

Microsoft Surface Book 2 (13.5")
Pros & Cons:

Spoiler

Pros:

• Highest screen res of options I'm seriously considering
• Great battery life (when used as a laptop)
• 512GB storage
• Decent pen
• Proper keyboard
• Bonus - discreet GPU in keyboard unit

Cons:

• No LTE connectivity
• Fairly pricey
• Not sure how well the battery will last as a tablet

Lenovo Thinkpad Yoga X1 Yoga
Pros & Cons

Spoiler

Pros:

• LTE connectivity
• 512GB SSD
• Optional OLED screen (albeit at a steep price hike
• Good battery life
• Pen, which docks for bonus points

Cons:

• Non-detachable keyboard
• Gets very pricey when bumping up all the specs

Panasonic Toughbook CF-XZ6H
Pros & Cons:

Spoiler

Pros:

• Theoretically ticks all the problem boxes - 512GB, pen, detachable, LTE
• Secondary battery in keyboard dock, which can be replaced/spares can be carried
• 'Business rugged' - designed to withstand desk-height falls

Cons:

• Extremely limited availability in UK - business resellers only
• Only the 256GB variant seems to be available, not clear if the 512GB model can be ordered
• Battery life without keyboard dock questionable
• Quite pricey

So the question now is, what do I do?
Do I compromise - if so, on which area? Is there another option I've overlooked? Do I wait and see whether the likes of Windows-on-ARM offers up any compelling options?

Any input/suggestions would be greatly appreciated.