I still read "manufacture" as paying the cost after the casting. Besides that - stock up nine mana over several turns, for a net +2 cards? I like it.

Think I made the reminder text a bit more clear. Better?

It does, though yowsers on the word count.

I could probably remove the “if you do”

An alternative based vaguely on suspend. Still longish. Your choice of counter will vary.

(Rather than cast this card from your hand, you may exile it with N ice counters on it. It gains ": Remove an ice counter from ~." When the last ice counter is removed, cast it without paying its mana cost.)

To be honest, if you got a lot of Manufacture cards, you should probably be using counters anyways. It would let you interact with them a bit more too. For example, a creature could read ": Remove an N counter from each card you control in exile."

I fully expect players to use counters to keep track, but I like the mechanic as it now stands. Since I’m not actually going to be printing and selling these, I will assume anyone playing with it will be using counters anyways. The set isn’t intended to be played alongside anything else, and there are very few cards that exist interacting with counters on exiled cards. Oh! You actually just gave a good idea for a card though.

As it stands, I feel like this reads less complicated than a suspend variant, so long as I presume players will keep track with counters.