Best to approach this as a complete system, then plan on jumping-in with both feet and redoing the wiring from scratch, over 2-3 afternoons. Adding leads for the front signals, along with whatever leads are required to integrate your bar-mounted switchgear is going to mean more work than you realize, at the moment. And that bundle to be threaded into the frame is going to be fat. IOW, essentially, you're going to rewire the whole bike anyway, in the attempt to "save time & work" and "not disrupt anything". Hindsight will come back to taunt you...ask me how I know this.
My suggestion, save this for a time when you won't mind having the bike out of action for a while. 2 day's work can take weeks, when your job demands top priority on the schedule. Use the same switchgear & wire harness as in your cruiser bike, source an electronic flasher relay, amber LED bolts for the the license plate, for the rear signals, and whatever suits you for the front. With 12v electrics, you've many choices. That's as clean and reliable as it gets. The "difficult" tasks will adapting keyswitch leads and lengthening some of the leads to the front end...a bit tedious, but straightforward, stuff.
With the engine topic...you've just rediscovered what I did circa 2000. At that time $1900 seemed outrageous for a 110 Nice motor...until you started adding-up all the parts needed to build a Kitaco, or Takegawa, 110-124. Until 2002, even a 160 Nice was a lot cheaper (low $3K range). The TB 110-117 stuff didn't exist yet. There's still nothing out there that compares to the Nice lower end & electrics. A few years before this board was created, 60mph was the small bike equivalent of "doing the ton" (reaching 100mph...in Britspeak). Top speed potential increased almost overnight, but it came with a cost curve that resembled the power requirement to reach those increased speeds...including the one factor few seem to grasp, cost per mile. There was another evergreen discussion topic, along with "
what's the best oil?"..."
how much we're willing to spend to get another 10mph" That one was a heady mix of truth, enthusiasm and wry humor. A reliable/reasonably durable motor, capable of sustained 60-65mph cruising, is going to take the kind of bucks you're talking about, at a minimum. When the service life, between rebuilds/repairs, is factored-in, a 127-146 Nice won't cost any more...might even have the lower cost-per-mile...but you're still talking $3K+, depending upon the options selected. And, the operational characteristics will be different. At any power level, the 49cc-based tunes will be revvier, with less torque...and still based on a 49cc lower end, including the tranny. The Nice-based tunes, including bone-stock, will be torquier and with lower ends that are unmatched. What's the "best" motor...there is more than one answer and no answer. It's up to guy writing the checks and riding the bike. IMO, every choice will have at least one compromise and the decision can be at least a little painful...a strong argument for having more than one bike, each purpose-built. Come to think of it, isn't that what keeps this hobby interesting & engaging?