Homebrewed X to Y Stat 'Mutations' how wrong can this go?

[EastbySoutheast]

Okay so my regular DM has decided he wants to play a mutant campaign and has set out a load of things that you can select by taking penalties to various ability scores. You have to roll 3d6 and enter the results in order to the attribute scores as they appear on the character sheet.

A simple example of what hes proposed is:
Each point of Dex minused =+1 Con
hes also provided a way to entirely reduce all mental skills (Bar INT) to 1 and move them all onto strength.

I feel this system is kinda flawed and results in some fantastically unbalanced characters. How badly can this go?
So far i have a character that deals 3d6+20 damage at level 1 but i want to know the playgrounds thoughts

[ZamielVanWeber]

Maximum dump stats ahoy! Anyone not using charisma can just dump it to 3, get a massive boost to another stat and then have a solid excuse for never roleplaying. I feel I need to note that Int 1-2 is animal intelligence. There is a reason things that lower Int say "min 3."

I also feel this is somewhat unfair to charisma casters; anyone else can just not use charisma and eat it up entirely, but charisma casters need a touch of strength for their items (not a lot, but certainly not 1-3), enough Dex not to be hit by literally everything, enough Con to instantly die, 10 Int for their precious skills, Wis adds to Will (and is thus probably the most dumpable stat) and of course they need charisma.

[ExLibrisMortis]

You could make a fun charisma SAD build, using paladin, ascetic mage, sorcerer, walker in the wastes, marshal and so on. Charisma to EVERYTHING!

Fun fact: Horned harbinger 2 (Faiths and Pantheons) actually gives you +cha to caster level for animate dead. Dread necromancer 8 gets you +cha to the number of HD you can control per caster level. DN 8/HH 2 gives you (4 + cha mod) * (10 + cha mod) HD of undead you can create and control in one casting. With a point-buy like that, you can get 50 charisma and control 24 * 30 = 720 HD of undead, at level 10 (enough levels left to become a dry lich and get cha to hp). And that's not even with CL boosts, like consumptive field, practiced spellcaster, ioun stones and whatnot.