It is defintely viable if you have previous experience. There are more and more online programs available for home training, from JKD Chinatown to Gracie Acadmey's "Gracie Garage" program.
I attend a Gracie Garage. The guy who runs it did MMA for 3 years and his main training partner is a Judo Black Belt, so they are great guys to train with. The Gracie program is great. I recently went to a BJJ class and the instructor said my positional control was as good as he'd ever seen for a white belt. Now I should add I did a few years of Judo so that helped too ha ha!https://www.gracieuniversity.com/Apply.aspx?enc=b4am/VqyoYdfbD8Fg4TD/w==
A blog you might want to read is from this guy. He was a long time practioner of Shotokan and he quit. He gives his reason for quitting. He also states that he does PX90 at home now and he is much fitter and stronger than when he did Karate. He said for him Karate began to deman too much and offered too little in return. Interesting blog and it shows you're not alone! http://dysfunctionalparrot.com/5-things/karate/