are t-taps or scotchlocks suitable ?

excellent point about the small piece of metal inside a 25 amp fuse, or even a 30amp..

along with 12 years of installation experience and running my own business for 8 years, successfully, i also have a 2 year degree in electronics

a ttap is not used for high current, however, i want to see a remote start continuosly supply  25 or 30amps of current..     in high power car audio systems, yes, in remote start or alarms... NEVER..

any increase in resistance due to the supposed restriction of a connector, will be negligable... if you were to run your ignition wires on 16 or 18 ga for a great distance, then yes, you would have problems with wires heating up from increased stress when there is less resistance..

keep in mind, the thicker the wire the more resistance there is, however, in DC thicker wire allows current to flow more freely

exactly the opposite of AC

in fact, a connector, would lower the resistance value before it would increase it......   lower resistance equals increased current flow.. increased current flow means heat..   kind of like putting a wrench across battery terminals

either way, we all have our opinions, i used to solder, i used to twist and tape, i also did CODE ALARM type connections... all very time consuming without any benefit..    i spend about 60 to 75 minutes on alarms with remotes starters and have yet to see a car catch fire....

In fact, my single most expensive mistake , 7 years ago, cost me $114 when i burned a keyless entry module...  followed by a $10 lock switch,, in twelve years, i think that is pretty good.