Unless I missed this suggestion, how about finding a kiltmaker who is willing to sew permanent pleats into your pre existing great kilt? It would at least make it easier to put on though it doesn't really make the garment itself any more practical to wear.

I know that Chris from www.southerncelt.com offers such a product. He seems to have disappeared from this site and just now I was unable to access his site... Perhaps another kiltmaker here would be willing to assist in this capacity?

Another option is to have this tartan material fashioned into a large shawl and fly plaid [kind of a his-and-her thing] and have a traditional kilt made in a matching plaid. Just a thought.

Mychael