Building a cat hotel

Here in Texas, we recently had a hard freeze (got down to single digits). On our front porch we had some chairs. I took the seat cushions, put them under the chairs, hung a halogen bulb between the chairs, then covered the chairs with a couple of sheets, to provide the local ferals with a warming station. It worked, but maybe too well. We have three ferals (who we had previously trapped, spayed, and released) who now sleep there every night, even though it is no longer cold. So we basically cannot use our front porch anymore

Has anyone every built a cat hotel? I want to make it two level, with dividers between cushions, so that it house four cats, have wooden sides but canvas front and back, so that cats can get in and out of it in a hurry, a solid roof so that it stays dry even in rain, and a space where I can put heating bulbs to keep it warm in the winter. May main concern is that I go through all that, and the cats find it unsuitable

Has anyone ever built a cat shelter for the local feral cats?