you ask "What else can drive it up?" perhaps without realising you've answered your own question in the first 14 words of your post.
PLS went from 1c to 70c without putting a gram of dirt on a ship. APT is up 400% whilst generating losses (currently). the concept that a company's valuation is based only on revenue is completely wrong. especially in resources. (disclosure bought more PLS Friday, have never owned nor interested in APT.)
The company's I've mentioned have had a s/p increases which are predominately based around potential earnings, growth and revenue. AVZ's market cap is one a culmination of 2 basic factor; the first being that the market is not convinced this will not be mined and the second being that a portion is convinced but greed of lower entries.
As you've rightly indicated at the start, there are obstacles which are required to work through. I.e Proving profitability through DFS, securing funding, then construction and commissioning of plant in time, then subsequently operating that plant.
it's a pretty simple recipe, take a larger risk and invest earlier. or take lower risk and invest later. (you make the call on what the s/p might be at those junctions also note, being in production doesn't guarantee success, (GCY for example) they were worth more as an explorer. then moved to production when it didn't meet expectations, it dropped drastically. *(disclosure previously held and traded, looking for potential re-entry)
AVZ's a pretty simple formula. but it's reward doesn't warrant the risk for many investors. I for one have a differing opinion that the more riskier the stock the more undervalued it is. the same way I identified property as an overvalued asset 5-10years ago, because everyone seemingly saw it as the safest thing to invest in.
I think that the perception that a stock is supremely safe in-fact makes it more of a risk (as you're essentially paying a premium for security based on nothing more than the collective and usually uninformed perception of the population). the banks (see gfc), property is Aus (still going nowhere), gold (looks like it may be making headwind) all seemingly impervious defensive choices. yet timed wrong could have major losses or only breaking even after years of tied capital. and usually substantial amounts.
AVZ has always been a 5 year play for me, it now has 3 years left in the timeline, by 2022 avz will either have went into administration, will have been bought out at a premium, or will be part owner/operator (at some capacity) of a globally disruptive lithium producer.
given that tailings (sat on manono tenements) of 1/20th the size (100mT) and 35% the grade (0.5-1%) of manono were acquired for our current market cap by a shell controlled by our largest investor. I'm pretty confident that management could sell us tomorrow at our current price. the obvious desire not to, being that they believe it's worth a lot more.
that said, it doesn't mean the price can't half next week.