There are lots of folks around here that can help you out with such a venture, though White Knight (
http://whiteknightminiatureimperium.blogspot.ca/ ) is likely the man to ask about such questions for personal ventures. Clam has done similar things (
http://claminiatures.blogspot.dk/ ) as well as Andy (manic_miner) from Four A miniatures (
http://www.fouraminiatures.com/ ). 4a is a business built out of a hobby.
I had a small lot of 28mm figures commissioned about a year ago. The price you will pay depends on the sculptor - the more 'pro' they are, the more you can likely expect to pay. A typical estimate is about $10 per mm of miniature for a single pose, human sized model. Again, this can vary widely. If you plan to sell them to recoup your costs (a lofty if not foolhardy goal) you will likely want them in metal. I know that most of the kind folks on LAF would prefer metal to resin anyway. Metal is cheaper for bulk production, whereas resin is cheaper if you only want a few casts for yourself.
I forget the price I paid at this point, but for metal, you can typically expect to first have the sculpts made into a 'master mould'. This will cost somewhere in the ballpark of $100-200ish? From that mould, multiple casts of each piece will be made to make a production mould (cost unsure, probably similar to the master). The production mould is what is used to cast your figures for general production, and once it deteriorates it can be made anew from the masters.
It really depends on your vision and your disposable income, but multiple parts can make the cost skyrocket astronomically in very little time when you consider it will take more sculpting time, and more fiddling to make it all fit together (especially due to expansion/shrinkage during casting). Single pose figures will be cheaper to produce, and you can make some nice dynamic single pose figures you could not easily make from a multipart kit.
Also, this reminds me, White Knight does have not-Empire knights in the works which he purchased from fp, another member on Warhammer-Empire. Perhaps not super-ornate though.
As for sculptors, ask around here. I know there are a few working who do freelance work. Otherwise, there are sculpting forums you could frequent to post up an ad. I know Mark Evans was the sculptor for WK's landsknecht sea-elves, and those are probably the most ornate of his figures. There are also the Lead Adventure Miniatures knights
(link) being sculpted by Ratnik which might just be released in the new year - those are quite ornate and nice. Would not mind seeing Ratnik sculpt some more in that vein...