I've built two wood gasifiers before. My experience with them is that they are finicky and dangerous. The first one was made out of a charcoal grill and a small metal trashcan to power a chainsaw motor that ran a generator for some camp lights (basically i wanted to be able to fit the whole system on the back of an ATV and take it all over my property). It worked well, but then it would start running low when it got to the end of a batch, it took a long time to get started, fuel was wasted when I wanted to stop, etc. The normal problems with a gasifier. The second one was also to power a generator and it caught on fire the fifth or sixth time I used it (user error, I know, but its still not a fun experience).
So in my opinion, yes, a wood gasifier CAN be a viable source of fuel, but only if you know exactly what you are doing and you are prepared for failure and a finicky operation. In other words, there are better options.