I see a few flaws in your reasoning.

Yes, any IC will have a pressure drop. But cheap (sub $300) china A2A IC’s have a much worse pressure drop than a quality core IC. This makes a huge difference in IAT temps as the turbo has to make 3-5 additional lbs (or more depending on boost level) to get your desired boost at the intake manifold. Some of the China cores are so bad I’ve seen setups make more power removing them completely. As you pointed out weight and space is a factor, don’t forget cooling. Putting an IC in front of a factory radiator drops the cooling systems efficiency a ton . Many times this results in radiator and fan upgrades. (expensive) It will also block air going to you’re A/C condenser. Since you seem to be against water/meth, have you considered a small A2W IC? You could remote mount it and the A2W cores tend to have much less pressure drop across the core. A lot of weight and hassle for your power goal IMO, but there’s no arguing that they work well.

As far as meth kit cost reliability goes… The performance per dollar/time invested with a meth kit is the best part. They are dirt cheap when compared to a “good” A2A IC and the amount of work it takes to install one. At low boost levels (like you’ll be running) they work better than an IC IMO. For “Bells and Whistles” I run an AFR safety system. If the AFR doesn’t match my target table with a half point or so the ECU drops IGN. (can also be setup to sound an alarm, trigger a light, etc.) Not sure what your using ECU wise but AEM’s WB02 sensor/gauges have the feature as well. I’d want this safety feature whether running alky inj or not. It would cover your safety worries either way. As far as cost goes you could put together a simple DIY meth/water kit for about $200. How far you can push it depends on the amount of methanol you spray IMO. I always had the best luck using 100% methanol and spraying LOTS of meth. A 5.7 reving to 6k at 10lbs should spray about 20GPH of straight methanol or 10gph of 50/50 water meth mix at the throttle body. To aid a bit in charge cooling I’d placing a few tiny 1-2gph nozzles along the charge pipe length and 1 pre-turbo. That would be more than enough for a 500hp pump gas LS1 setup IMO.

Been drag racing turbo street cars for 15+ years. (new to LS world though) I wish it was as simple/easy as just “preloading the turbo”. It’s all a balancing act. You want to run the tightest converter possible, especially on a street car. The more volume and pressure drop you have in the system the harder it is to “get up on” the converter to get the turbo spooled. This is made worse by the heat loss with a remote kit. Throwing a loose converter in the mix will build boost off the line. It will also cause excessive heat build-up and more slippage across the board resulting in slower trap speeds.

Your 4cyl to 8cyl argument would only be valid if the charger size stayed the same. The size of the turbo is relevant to the size of the motor. A turbo small enough to light off instantly on a remote mounted “v8” will choke the motor severely in the upper RPM. Again… it’s a balancing act.