My goals this offseason are to (i) maintain my bike fitness and very slightly increase my FTP; and (ii) use a simple weight training program to just get stronger overall.

Question - is it a bad idea to squat 3 times per week in addition to riding 3-4 times per week? In other words, it seems like I'm working my quads 6 days a week, so is this plan too squat heavy?

I've been doing this for the past 3 weeks, and I've loved it. Stronglifts is super simple for a newbie, has a free app that guides you along, and I'm just now getting into a bit heavier weights.

Here's how it looks right now

Monday - Stronglift 5x5 workout A. Run 45 min zone 1-2
Tuesday - Bike
Wednesday - Stronglift 5x5 workout B. Run 45 min zone 1-2
Thursday - Bike
Friday - Stronglift 5x5 workout A. Run 60-70 min zone 1-2
Saturday - Bike 1.5 hours
Sunday - rest or very easy Bike

Stronglift 5x5 Workout A - squat, bench, bent over barbell row (each 5 sets of 5 reps)
Stronglift 5x5 Workout B - squat, overhead press, deadlift (each 5 sets of 5 reps, except deadlift is 1 set)
Note - the Stronglift workouts just alternate each week, so one week to you A,B,A and the next you do B,A,B

Cheers everyone.