You still did not answer to my question.

Do you already have the display (the LEDs) physically available? If yes, where is the schematics?

If not, do you have the budget to build it? I'd assume, for this size, your material cost will be in the order of $1000 to build a prototype.

Also, what is "a line"? Do you mean a line of text, or a line of dots? In the latter case, will you need arbitrarily slanted line, or just a horisontal and vertical one?

JW