Monkey Math Madness

So, ignoring most of the Jokaero's stuff, let's look at their upgrade table:

1. A waste, obviously.
2. 12" range boost- this is pretty fantastic for a lot of our weapons, like Meltaguns, Multimeltas, Storm Bolters, etc. Note that this doesn't change your Rapid Fire range at all and doesn't help template weapons.
3. +1 to armor. Also very nice, but doesn't affect the Jokaero themselves. Still, you get a free upgrade to Carapace, which will keep you alive against Flamers. Note that, if you want to shell out way too many points, you can buy Power Armor for your Acolytes, which turns into Terminator with this. 14pt Terminators ftw!
4. Rending, the other super-good one. Doesn't help your Meltaguns any (except to penetrate Land Raiders even at 12"?), but very nice for guys with other weapons.
5. 5++ save. Meh, you're already wearing Flak and should be in cover.If you get into CC with some power weapons, you're boned anyways.
6. Two upgrades, but you can't get a six again or doubles of anything.

So the way that this works out is actually sort of awkward; +1 on the chart per Jokaero beyond the first very quickly makes it likely that you will get two rolls, but those rolls become very likely to do nothing, as the bonuses make you get more results of 6+, which does nothing. (Unless that gets FAQed, which given they're an Imperial codex is not beyond the realm of possibility.)

So the ideal number of Jokaero in a unit, if you are trying for good upgrades, is two; this yields +1 on the chart, guaranteeing you can't get the useless result of '1' and gives a 1/3 chance to get two rolls. Note, however, that your two rolls each have a 1/3 chance of doing nothing (i.e. getting a 5/6, both of which translate into the blank "would roll twice again but can't") as well as the chances of rolling doubles (which does nothing extra, but at least gets you some benefit unless you roll double fives or sixes.)

Coincidentally, two Jokaero also meshes well with both a Rhino's fire points (letting both of them shoot out the top) and a Chimera's (letting the two of them plus the three Meltagun-toting Acolytes shoot out), which is very convenient. So a couple setups I like the look of (note: these are not necessarily good, as I haven't studied the GK codex a ton yet):

2 Jokaero
3 Warrior Acolyte w/Meltagun
(other models to suit, possibly some Warrior Acolytes w/Boltguns)
Chimera

Five Melta weapons shooting out of the top hatch, with about a 25% chance of getting the +12" range upgrade, which is the best you can hope for. Unfortunately you don't take much advantage of the other bonuses unless you add some guys with Boltguns (or, if you're feeling saucy, Storm Bolters); five Storm Bolter dudes sets you back 35pts and potentially gives you ten shots out to 36" on turns that your Chimera moves, assuming you don't want to use Meltaguns.

2 Jokaero
1 Warrior Acolyte
Rhino

Upgrades? What upgrades? You can spit out Lascannon or Multimelta fire as needed, and if you happen to roll up +12", all the better. If the enemy comes in close, a pair of Heavy Flamers is bad news as well and with Rending they become pretty ugly.

2 Jokaero
3 Servitors w/Multimelta
3 Warrior Acolytes w/Flamer
Chimera

You kind of overpay for Flamers in this squad, but given they can be Rending (25% chance, as usual), maybe that's okay. You have either five templates or five Melta weapons coming out for this thing, and your chance to roll one of the two "best" benefits for this squad are rather high. You could potentially add bodies to this squad to make it more resilient as well.

2 Jokaero Weaponsmith
10 Warrior Acolytes w/Boltgun

No, I didn't forget to give them a transport- this squad sits on a home objective and annoys people. Unfortunately They're not super-cheap, but at 120pts they're not terrible, either; attach an Inquisitor or other character and they won't break often. You're really banking on rolling up either Rending or +12" and then pretty much hiding in cover; if you sink another 20pts into the squad you can give them Storm Bolters, which can drastically increase their firepower output and makes them something of a pain to deal with for many armies if they roll the +12" upgrade.