Yeah, so that 15% off the lowest price over 6 months is an awesome deal. And assuming you’re out of non-mortgage debt, I would definitely be maxing that out.
I think the “correct”/most likely path to the most wealth is to sell it all as soon as you’re allowed (or possibly after a year to get to the long term capital gains tax rate) then put all the proceeds into index funds.
The reason is that the market is “efficient”. Everything you mentioned about your company (important over the next decade, seems like a good price) is known to everyone else in the market too. All that stuff is “priced in” to the market. You can’t reliably predict this stock is going to outperform the market. If you could, everyone would go buy it (and sellers wouldn’t want to sell it) until the price raises to the point where you can no longer predict outperformance. That type of adjustment to all available information is happening instantly and constantly in the market.
So when you’re putting money into a single stock, all you’re doing is increasing future volatility (single stocks go up and down faster than entire markets) without an expectation of higher future performance. That’s not a good trade.
THAT SAID, that’s the rational/“correct” strategy. And I get that you want to take a risk. Especially if you work for a company you believe in. Personally, I made a lot of money buying stock of the company I worked for… my only regret is selling it. So if you want your “lotto ticket”… the chance at large outperformance, I think that is reasonable. But I would never put more into a single stock than you can afford to lose and still have your retirement in good shape. i.e. if you’re investing enough outside of this stock to comfortably retire at an age you’re happy with, then sure throw some of the extra in the stock… so you’ve got the sure thing and the lotto ticket! 
