Value changes to most existing entries in the raws shouldn't require a regen. Only those that affect worldgen will require it (biomes and entities).
You can try putting [CAN_STONE] onto your picks and add [SHARP] to some more stones to better balance out play for the gnomes. Flint and chert come to mind immediately as relatively sharp stones (although perhaps not up to the task of cutting other stone), but perhaps something like a fine grained basalt would be more appropriate (the stone of choice for carving giant Easter Island heads).
Alternately, you could allow gnomes metalworking skills but give their entity the [MINOR_METAL] tag to limit them to copper, but I've never tried that with a player civ before, so I'm not sure if it would work or not.
Another option could be designing a smelter reaction to turn some type of stone directly into a pick...
Thanks for the advice. I made flint and chert [SHARP], but because I started off with 2 picks, and wanna make it a little harder on myself, made it so they can't make any more. I might try giving them [MINOR_METAL] a little later, for science!
Plus it does make sense, at least the way I see gnomes (That is, little cousins of the dwarves, who would have learned SOME metal working from their kin)
Thanks for the help all!
edit: Never...EVER... embark as gnomes on the site of another gnomish civilization....Gnomes apparently hate stegosaurs with a passion and will drag your poor 7 into conflicts they CANNOT WIN.
Dead Stegosauri: 18 (8 named, 1 named and titled)
Dead Gnomes: 26 (1 mine) + 1 stray dog
Surviving Stegosauri: 4 (2 named)
Note: Gnomes can still use armor etc, so most of those dead gnomes are wearing full suits of -iron- armor and wielding *+=iron maces=+*. The mayor is all supermountain gnomely stats and is currently lying in a pool of his own blood, vomit and chunks after trancing against a single stegosaurus...
edit2:Oh no....Duck-Billed dinosaurs....