^like he said, tinker gnome.
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well...it's "interesting"
i don't think the RDD benefits really pay off enough to balance out the losses. +4 Str, +2 Cha, yet you effectively lose 2 str and 2 cha for going gnome (vs another base race). that alone is barely a net gain, basically +2 Cha in exchange for being small, which isn't really much of a benefit at all for a smiter that isn't a x2/PL reinc going for 2h rapier (+1AB/AC in exchange for using small weap..."mehh" not terrible I guess). on top of that, level planning is looking a bit annoying due to a few factors: a) 16BAB by L20; b) needing 13+ Str for PA/Cleave->BG, and relying on rdd +Str as an advantage, yet gnome's inherent Str (and cha) pen makes it a comparatively bigger waste of points to get Str (and cha) up in creation. well, at least the tinker gnome +2/-2 Int/Wis evens out.
playing around in notepad i came up with
Str 14
Dex 8
Con 12
Int 10 (+2 gnome pts, and +2RDD Int should be solid amt. of skills, at least that's a plus)
Wis 14
Cha 16
edit#235345: actually i forgot to apply tinker gnome changes too, that's just creation window stats. so really have to drop con and int for +2 more wisdom to still hit 14 after -2 pen. ouch. such a shame to waste all those creation pts tho...maybe better off just going great wisx2 in LL feats instead, not like having L3-4 spells gonna matter very much till then anyway. then it's tradeoff of +1dmg/AB(from x2great str--really don't skip BF for cleave->OC/DC imo) for +2 con worth of hp (in pre-LLs where it matters) and 63skillpoints, which should make up the difference anyway.
1 sorc power attack
2 rdd1
3 rdd2 cleave +2StrRDD(16)
4 rdd3 +1Cha(17)
5 rdd4 +2StrRDD(18)
6 rdd5 WF(light mace)
7 rdd6
8 rdd7 +1Cha(18)
9 rdd8(now have +6BAB for bg) GWF(light mace)
10 bg1
11 bg2
12 bg3 +1Cha(19) Div Might
13 bg4
14 bg5
15 bg6 ImpCrit
16 b67 +1Cha(20)
17 bg8
18 bg9 blind fight (well, listen gonna be bad till VoV/reinc/aug/PLs in whatever order soooooo...or if u wanna rely on C/C Listen w/no LSA, go great cleave)
19 bg10
20 rdd9 +1Cha(21)
just barely hits 16 BAB in time.
overall it's workable I guess. 7 base epic + 6 BG epic is 13 feats to play with, 10 greatsmite + 3 spares, the standard. tried a few diff feat progressions but unfortunately there's no real practical way to hit 25 Cha from levelup alone with enough time left over to take all 10 GS, without burning epic feats for Great Cha. Going higher start Cha results in issues pre-epic. Could drop Con ofc, and Int, 10 con open sub "Str" tank is lil weak tho, and I think the extra skillpoints at worst evens up with another potential +1 Cha to be gained from re-arranging creation stats. This is one progression I looked at (very painful but not many better options sadly)
21 rdd10 +2ChaRDD(23) GreatChaI(24)
22 bg11
23 bg12
24 bg13 +1Cha (25) GSI, GSII(BG)
25 bg14
26 bg15
27 bg16 GSIII,GSIV
28 bg17 +1Str(19)
29 bg18
30 bg19 GSV,GSVI(BG)
31 bg20
32 bg21 +1Str(20)
33 bg22 GSVII, GSVIII(BG)
34 bg23
35 bg24
36 bg25 +1Str(21) GSIX, GSX(BG)
37 bg26
38 bg27
39 bg28 EWF, Armor Skin(BG)
40 bg29 +1Str(22)
This leaves you going into LLs without Prowess, not to mention the typical "non-reinc smiter" low Str, even after +10 from Great Smite unlocked. This build would be pretty fail to try levelling with, AB would be a joke. Due to gnome, rapier wit is a no go, although it would be hilarious to watch a x0 gnome 2h rapwit get pwned in LLs (jk, we've all seen it at least once I think, and it remains hilarious for about 2 spawns). Of course could just dump everything into Cha and abandon Str for that idea. Smites are going to really be crap with bare minimum Cha and -11 AB from class spread too (which is another inherent flaw in this class breakdown concept). Either way, due to being a Str-poor "str tank" while levelling, maybe reinc @40 from a "normal" Str sword/board bg. Anyway LLs looking rough too, can do Epic Prowess, LWF, LSA Tumble, +4, I'd do extend, Great Wis->15, x2Great Str I guess or OC/DC if you did great cleave earlier... LL stats into Str, can at least hit 40 base before 60 lel.
overall I don't really see this as something recommendable for newbie (fine for bored fun openrace experiment project i guess), at best it's basically an open sub human smiter w/ worse smite AB and worse weapon, or an open sub half-elf smiter with worse weapon, worse smite AB and no LSA Listen, but it's a funny concept. bonus points for being a dragon? hard to say which is fuglier, a dragon or a gnome...

prolly best to leave open sub smiter (which will be trash no matter what honestly) to human or half-elf base. Gnome+non-divtank subrace stats just doesn't add up to a strong divtank candidate, with RDD +stats not really making up the difference after considering the extra hassle of carefully playing with BAB and feat breakpoints, and again the -11 smite AB ofc, and last but not least 8 base dex deserves an honorable mention--dex gonna be bad regardless for "open sub smiter" but 8 is going from bad to wors(t).