suracha,
A bit late but as no-one else took a shot at this one..
I think your best option may be to look at two separate hosting companies, one doing linux, one windows, and just sell through both. handyhosting and hostcaters (windows then linux) are two I could recommend to you. I've spoken to both the owners on many an occasion and both are very commited to making sure their customers are happy.
We're actually looking at using handyhosting for windows accounts. We don't have enough of a call for it to go and set up a box, but with a few Ultradev developers on our books it's something they may find interesting.
All you need to do is register another set of nameservers for your domain. Run the first two as linux, the second two as windows. I may get a little funky if you don't keep an eye on who is on which server, but a little book keeping will take care of that
Greg Moore