In my mind this mix is obviously just wrong, yet still I find myself wondering...
If one was to throw a level of Sorcerer into a Wizard (built stat-wise to be a wizard, no extra in cha) would this wizard then gain the advantage of the double spell points Sorcerers get from items giving them?
Nope. Any multiclass of X/Sorcerer gets a percentage of the double SP bonus. So with 1 level of Sorcerer, you'd get 5% extra from items, which considering the best readily availbale is Archmagi, would be 200SP + 10 from your sorc level. If you were 10 Wizard / 10 Sorcerer you'd get 50% or 200SP +100. At least, I'm 99% sure that's how it works now.
I assume the spells chosen in the wizard levels will use Int as their modifier and the Sorc level would use Cha. I also realise that those spells would not be swappable except the one per three days.
Your Sorcerer level won't gain any spells, slots or charisma spell related stuff.
Another benefit to adding the sorcerer level might be the extra spell point enhancements, for example the first sorcerer one gives 30sp rather than the wizard's 20.
The miniscule extra SP isn't worth it at all. Once you start getting high level SP items, the Wizards hampered early level SP pool isn't such a hinderance.
I haven't checked it out but is the wizard's cap enhancement worth staying pure for? I see a lot of rogue/wizards so I assume not.
Multiclassing casters is generally a bad idea. The loss of Spell DC (how easy it is to resist your spells) plus spell slots plus enhancements and capstone (the Wizard is one of the best capstones) make it very detrimental to multiclass unless you have a very specific reason to do so. The X/ 2 rogue split gains Evasion and Rogue skills which is in some people's minds worth the trade off. Some builds do multiclass wizard, but they're usually higly specialised and have very stringent equipment and skill requirements.
Would a person be completely gimping themselves by trying this and how quickly would they be laughed off the server
Yes. People would probably assume you were a very old build (way back, you could get double SP from a 1 level sorc splash) and will be wondering very strongly why you hadn't rerolled. If they knew you deliberately took 1 level of Sorc on a Wizard, other casters will write nasty things about you in the bathrooms.
Or maybe... has anybody tried it already?
(Open to the obligatory flaming.)