What makes con "dump-able?"
is it safe to interpret that despite the handicap of having 3 int, this only means that maybe up to the mid-game I'll suffer penalties to the crafting stats which otherwise is negligible in the late game? I'm a little torn on how to invest on my stats at this point
If I'm following you, either dump or pump into a stat and never go for a safety 4 or 5 to off-set penalty, correct?
Yeah, I'm trying not to give you a cookie cutter and just tell you to press it into the dough, but that does mean I may be giving you enough options to be largely unhelpful.
OK. Con is dumpable when you either have a way to not get hit, or a way to not take dangerous damage when you get hit. You can not get hit by attacking from range; by alpha striking so hard you murder everything before it can go; by exploiting line-of-sight against ranged enemies and physical space against melee enemies; by reducing the ability of enemies to successfully hit when they attack; by preventing the enemy from seeing you to attack you. You can take no dangerous damage when you get hit by having excellent armor against whatever damage type is hitting you; by having very high-capacity energy shields; by using Aegis and Morphine; by having such an immense HP pool that damage is largely irrelevant (aka playing on Easy). You see, there are a lot of options for what sounds like a very simple thing. If you want to play a stealthy SMG type, you're going to need to leverage stealth (no use against robots and true-sighted enemies), dodge/evasion (not deterministically reliable but useful to limit damage to spikes rather than plateaus), line of sight/physical distance, and energy shields. Maybe also Aegis/Morphine. If you can envision a game play concept where you will always be able to do at least two of those things then you can safely dump Con.
As you go through the game, you will eventually be offered a house in Core City. There will be many options for you, when you have that house - but one set of those options will include moving in workbenches which will provide a +15% buff to your effective crafting skills. At 3 Int, you can still get high enough effective skills to craft whatever you need, in your house - especially if you have access to Hypercerebrix (brief +2 Int buff). With low Int, all you really lose access to are crafting feats, but for a gunner, that's not a huge deal since Gun Nut is notoriously underperforming, and Skinner/Clothier/Ballistics are all very modest improvements, at best. Since you only have three skills that you really need to max out (Guns, Dodge, Evasion), and a few more that need less than half investment to cap their actual usefulness (Hacking, Lockpicking, Traps, Mercantile, Throwing) you'll have enough points that you can spend (skill points) your way to crafting success despite having an effective skill penalty.
Correct. UnderRail hugely rewards specialization and min/maxing of stats. Be good at something, or be really, really bad at it.