As Rolo above said - would be interesting to see if this can be done, so i would not change the rules regarding Specialists/Cottages.
Perhaps - just maybe - one possible exception: Allow to run other specialists than spy in one city for a limited period, with the specific purpose to pop a GP needed for a Corporation. Remember we do not have the option to pop a GP from tech, as we will never be first to something.
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Long post, sorry. To make the main point easier to spot, i translocated the conclusions to the top
Conclusions
If Sandard leader/civ's: I am still in favor of Louis. He seems to offer the best overall package form all standard IND leaders. And i think somehow he fits with the spirit of the game.
If Unrestricted: Rosewelt of the Summer.
Summer for Ziggurat (because it will help us rexing, and spying really early)
Roosevelt for IND/ORG. Even CHEAPER Ziggurat !!! 45

and the reduced costs for Civics - this should allow us some serious rexing while building up the Base of our espionage network at the very same time.
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And now, where tohse conclusions are coming from...
On Economy
Scientist-SE is working because of the beaker bonus under Rep, and because of the Techs that can be bulbed by popped GS. Both options we do not have in a Spy-SE.
Also because of the way how the espionage discounts work, we actually want to consistently outproduce every AI civ in Total Esp-Points, not just to create some bulbs.
On the other Hand: there are 7 regular (without wonders) spy Slots to be had in every city ( Courthouse + 2 * (Jail, Sec.Buero, Int.Agency) ) which is quite a lot. Plus the buildings give some base EspPts on they own.
On Culture:
We can't found many religions for multipliers (hepefully some will spread to us tho), we cant run Artists, and there is not much culture to have from slider. Just buildings/wonders are usually not enought.
So what's left are Corporations.
BTW.: Arborea - its one of those regional all land maps, isn't it ?... So basicly we can forget about Sushi... Which happens to be one of the culture corps...
On the bright side - no religions will be founded on the other continent
Strategy
We probably want many cities. Because:
0) We don't need to worry that much about our economy - we are not dependant on slider for teching.
1) Ressources (for Corporations). We need to grab as many as we can.
2) The Espionage buildings - each city can have them - we will not have quality commerce cities, so we might have to go over quantity.
I.E. early when the Courthouse is the only espionage source, more cities will mean more Esp-points - and by dumping a courthouse in a new city fast we keep the costs manageable.
3) Production. We will not be in tech lead - never - so we can't rely on more advanced units to keep up power rating, neither can we count on 'quantum leaps' - like beeing first to Rifling. So in the end we will need to be able to outproduce our enemies while at tech parity.
Midterm we might or might not have the possibility to extend our borders by attacking some of the Top Dogs (as we can't go after weak'ish civs).
So it seems that the
Initial Landgrab is very important, and should go beyond what would be called 'healthy ReXing' in most games - probably until the slider has to hit the ground.
Wonders
I don't think that we will go Wonder crazy on a large scale on the other hand there are a couple of wonders, which we really don't want to miss (Great Wall, Sistina, Statue of Liberty).
Leader/Civ
I will take IND as fixed - be it just to reduce the number of possible candidates. And i think even for those couple of crucial wonders it would be worth it.
So where does it lead us... My initial thought was Louis - IND/CRE + Salon. Did not concidered unrestricted at that point... Now after giving it some thought... I am unsure...
CRE hm... Helps a bit with the initial Landgrab - faster Boarderpops. But otherwise... 2 Culture does not harm, but is not anywhere near to be meaningful for culture victory. Cheap Buildings... Theaters are not that expensive anyway... Library - we don't need those.
Other interesting Traits
ORG (Rosewelt) - Helps a bit when rexing - via Civic upkeep. Cheep Courthouse - again - good for ReX but also good for espionage.
IMP (Augustus) - faster settlers... good for rexing, but i am not fond of it.
FIN (Huyana) - limited use without Cottages, but every little bit helps...
Salon - nice to have, but perhaps something to help us in the Early Expansion would be of more use...
Other interesting UB's...
Ziggurat - early, cheap courthouse. Cool.
Rathaus (HRE) - 75% of the Corp fees later... Not to sneeze on as well.
Conclusions - see above