My advice is based on various business and computer science training and a little experience.
I recommend producing and shipping an initial X8 system ASAP whether you offer DIY kit and/or preassembled.
Think about more than just the numbers you also need to consider intangibles those things for which you cannot directly assign dollar values.
For example people need to be able to get their hands on an actual system to stimulate them and keep up their morale so they will be willing to wait for an X16 system.
Be clear about everything involved with regard to a DIY kit and recommend it only to those who have more than enthusiasm they must already have experience with assembling such things otherwise you will have a headache and discouraged customers.
The emulator should be dropped right under their nose repeatedly so they are reassured that they can give the system a full go without handing over their wallet.
I am willing to buy a 'baby' X8 system and I bet many other former hobbyists and people curious about computer science are willing to risk it.