As one who thinks it's impossible to discuss the main typing without also discussing the secondary typing (because the secondary typing can so easily make or break a Pokemon), I will make my case assuming a couple of things.
I am advocating for the case of the Ground typing. Let's take a look at the top 10 individually and see what a tentative Ground typing will afford us.
Strategem- Renders his STAB quite useless. On Technician models you can hit back with your own STAB attacks which it is weak too, but on those same Strategems, you will need to watch out for Giga Drain. Ice Beam could be problematic too.
Revenankh- You may not do any super effective damage to it, but your Neutral typing affords you the ability to take hits from it (assuming we make this physically bulky).
Fidget- Resists his STAB Poison attacks, and hits back with SE damage.
Tyranitar- Resists his STAB attack, one thing of note here is that we should AVOID giving our Pokemon a Dark weak typing. Rogue Ice Beams could be problematic.
Zapdos- Immune to its STAB attack, and if we avoid giving this a secondary Ice weakness, or a Fire weakness, we shouldn't have too worry too much about HP Ice / Heat Wave.
Syclant- Oof, a huge Ice Weakness here, and it resists our STAB move to boot. This is one thing we might want to patch up with our secondary typing.
Blissey- As long as we give it some arbitrary amount of attack in order to 2HKO / 3HKO with Earthquake we should be good. Being immune to the common Thunder Wave is a nice feature.
Heatran- We're neutral to all of its moves, so assuming we have some workable Special Defense, we should be good. We could look into making the secondary typing one that helps us with this. Although HP Ice COULD make a dent in it.
Scizor- Neutral to all of its attacks, as well we are neutral to it... it's a toss up.
Pyroak- Ooof, huge weak point in that we are weak to its STAB move... not a lot we can do about this though.
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So we can potentially counter 8 / 10 threats... (not counting Pyroak or Syclant)
Now lets look at the potential secondary typings....
Normal- Adds nothing but the inability to counter Rev
Fire- We trade off our Rock resist for a Ground weakness and a neutrality to Grass and Ice and a Fire Resist... could be good.
Water- Gets rid of the Ice weakness, but excentuates our Grass one.
Electric- Ooof, this does nothing for us...
Grass- Like water, this could work, although this time we have an Ice 4X instead of a Grass 4X... plus we don't get a fire resist out of it.
Ice- Trade off our Rock resist for an Ice Neutrality and a fire/fight weak??? no thanks
Fight- I like this, we get a Dark resist, although we do get another Flying weak CAP
Poison- Let's not undermine Fidget.
Flying- We gain a Fight resist, but we make our Ice weakness worse... and we lose our Rock resist
Psychic- Gain a Fighting resist, but we also gain a whole host of new weaknesses
Bug- Fight resist, but also a Fire weak, and a Flying weak... do we need another one of those???
Rock- so overdone
Ghost- This could be cool, but we get that damn Dark weak again.
Dragon- Eh, i'm not seeing too much use for the added immunities... and the Ice weak is horrible
Dark- We get a Dark resist, but ugh... we get a damn Fight weak.
Steel- Dark resist again, and a buttload of other resists... we also get some nice neutralities to Grass and Ice.. but a nasty Fire weakness, maybe we could use the fire weak to keep it in check, don't know.
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So what I see, is that for viable double typings, we have Fire / Water / Grass / Fight / Steel
All of these have distinct advantages, and come with tradeoffs. I'd actually not mind a Ground / Steel type, but that's just me. Steel / Fight seem like the best options.
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But anyway, we can't have any of that until we have Ground, so VOTE GROUND