I wouldn't be too confident about seeing 'hilarious reactions'. At the very least there is a nice placebo effect from knowing that you are not fighting the ultimate 109, but instead his less slippery older brother. Also even a small reduction in top speed could raise the chances of allied flyers given that a certain 'flying Honda Civic' is so dependent on BnZ tactics.
As 109 variants go, I'd like to see a 109 F-4. From what I've read it was the most pleasant version to fly and could be included in scenarios for Western Europe, the Mediterranean, North Africa and the Russian front.
Naturally we'd also need some of its enemies from the same time period- LaGG-3 (yuk), Yak-1, Spitfire Mk V, early Typhoon Ib and so on. I'm not holding my breath.