British-style Ale Recipe Designing

I was reading in Tasting Beer: An Insider's Guide to the World's Greatest Drink tonight about brewers in late-1700s England replacing the brown malts in Porters with pale malt to improve efficiency.  Apparently some used burnt/candied sugars to darken their brews.  That would add to not only the darkness, but should add flavor as well.

The candi-sugar would have had a different taste and aroma than the brown malts it replaced.  These cadi-sugared beers would have had a flavor more like raisins or prunes. The old versions would have tasted more like chocolate or coffee.  Undoubtedly the darkest sugars used would have approximated some of the roasty characteristics of brown malt.

This got me to thinking about the beer recipe I've been creating.
PS - I did not drink these in one evening.

I want to brew an British-style ale, and the candi-sugar in the Porter story made me wonder what a brewer would do if they only had pale malt.  You would have to find tricks to make a beer look a certain way.  Things like using home-made dark candi-sugar in place of darker malts.

My starting recipe will be -

• 8 pounds - Marris Otter
• 1 pound - Candi Sugar (50SRM)
• 1.25 oz - Northern Brewer (60 minutes)
• 1 oz - East Kent Goldings (5 minutes)
• Safale us-04

I hope this will get me a dry, moderately bitter beer.  There should be notes from the sugar that you normally only get from sweeter, bigger beers.  I will mash the MO at 154­­°, that should help the beer from finishing too low.

Targets - 

• Original Gravity - 1.050
• Final Gravity - 1.010
• Color - 8.4 SRM
• ABV - 5.3%
• IBUs - 40

My test with this recipe is going to be the sugar.  I will replace the sugar with a darker variety each of the five times I brew this.  That way I can judge which sugar is the right color, and see how dark I need the sugar to get the color of a Porter.  I am going to make sugar for each batch, and make it darker each time.  I will follow the normal candi-sugar making method.

I am still figuring out exactly what the sugar should look like for each SRM.  I am hoping that I can simply shoot for soft-crack, hard-crack, clear-liquid, brown-liquid, and just short of the burnt-sugar stage.  The plan is to test out 50, 125, 250, 375, and 500 SRM versions of the sugar.  I hope I can get the 500 SRM sugar to match some of the dark malts, without having too much burnt flavor.

In a previous beer I was able to get very intense plum flavors, and dark coloring from caramelizing sugars, so this all should be possible.  The question I have is really one about taste.  Will the beers with the sugar still be in the style of the originals?  What impact did seeking better efficiency have on the beers of Britain in the late 18th century?