Strength Training - decent, bad, or terrible plan?

It really depends on what you want. If you want to maintain lifting and the muscle that comes with it, then that's what you should do. Just know that it will make your triathlon goals harder. It will take time and all the weight of the extra muscle will slow you down. It's not easy, but you can certainly do both if that's what you want. Lifting (for the most part) will not benefit your triathlon performance, that being said, triathlon performance may not be your only goal, so go with what is important to you.

In all honesty, I don't know what I want. I am new to the tri scene and endurance stuff overall. I have done sprint tris for a couple of years and survived them. I THINK I want to be a legitimate 12 hour IM finisher and think I have the bike and swim base to do it. I have to build a lot on the run. I am not a little guy by any means, but have always been a big strong guy as my view of fitness. More of a power lifter mentality rather than bodybuilder. Go lift as much as you can for 4-6 reps rest 5 minutes and do it again. And for years never even cared how to get to the treadmills and bikes.......

Tri is turning that on its head.

I have proven this week that heavy weights and tri don't really play well together. Tuesday I did a pretty heavy upper body workout and went to swim yesterday. Nothing long or fast, but trying a few drills rather than just swimming for 1500 yard kinda day. It was awful. I could not get shoulders moving right, could not breathe right and was considerably slower while doing them than normal, and really did not feel sore before I jumped in the pool.

I think between now and 20 weeks out from the full tri, I may still try to sneak in 1-2 days a week of legitimate weight training, but inside of the plan window, all weights will be high rep very specific tri helping!

It's a shift. I loved weight lifting, I think we like what we're good at. I was built to pull plows in the field. As said before, extra muscle won't help you. But you don't want to shift to lower weights, higher reps and not just 'cause it's boring. The training is your endurance work.

There is a world of lifting and strength work that is not isolated muscle building work. Look at Quick Strength for Runners: 8 Weeks to a Better Runner's Body. Using your body weight, moving in different directions, working muscles that don't get used as much to prevent injury.
Just because you're not lifting heavy weights doesn't mean it's not hard.

You want to think of different workouts for different phases of your training plan. The Ironfit books by Fink and Fink have some good ideas. I think they are the ones who talk about doing more plyo, explosive moves, again because the running and biking give you the endurance, this strength training gives you power, but it won't build muscle.

You can make changes according to your capacity to do training. For beginner workout you can go with, 20 body weight squats, 10 push ups, 20 walking lunges, 10 dumbbell rows, 15 second plank, 30 jumping Jacks, repeat for 3 rounds. For more details you can check out this site.