Actually, you could make that work. The deal with crouchers is that they tend to be pretty cryptic as they live amongst the branches of SPS heads. If there isn't such a shelter, they will find a spot in the rockwork. They really are best kept in a species setup as they don't compete well for food at all and are rather shy.
Feeding them can be a bit of a challenge, as you'll likely need to start the fish on enriched, small live ghosties or guppies. Once you get the fish eating for you, it's best to wean it onto small pieces of SW fish flesh, jumbo mysis, small bits of table shrimp, scallops, squid, etc.
Our last specimen used to hide in a cave and poke its head out when it was hungry, jump out, grab the food, and when full, it went back into hiding to digest the meal:
Coral Croucher Eating
Some specimens are less cryptic than others, but you get the idea.