How does my cycling training plan look for a beginner?

Hi all,

I've been putting more of an emphasis on my cardio work (as opposed to strength) and am loving it! I am new to cycling but I use the gym's indoor bike and have been seeing steady improvements in my pedalling technique and my legs seem to be adapting to the cycling training quite well. In saying that, I am still a rank beginner and probably only have 10-15 workouts on the bike logged.

My goal for this year is to maximise my cardio fitness (I'm using VO2 max as a marker here) and build power in my legs (FTP is my metric here). Primarily it is about getting as "fit" as possible with the time available to me, which is around 4-5 hours a week at the moment. My current training plan (AI helped me design it) is posted below and I would LOVE some insights from others as to how reasonable and effective this looks. I am also really curious about where most people think the diminishing returns for this type of work lie - if I increased my training to 10 hours a week would I see close to double the gains do you think? I feel like 10 hours a week is a hard cap for my on time and would require I sacrifice other things in my life but I could possibly do it if it was really going to improve my health faster. I assume it would mostly be adding Z2 work in so as not to overtrain? Anyway - training plan below, please tell me what you think. Thanks in advance all.

Session 1: VO2 Max Development

Warm-up: 10 minutes

Main Set: 

- 5 x 4 minutes at 105-120% FTP (245-279W)

- 3 minutes recovery between intervals

Cool-down: 5 minutes

Total Time: ~50 minutes

Session 2: Threshold Development

Warm-up: 10 minutes

Main Set:

- 2 x 12 minutes at 90-105% FTP (210-244W)

- 5 minutes recovery between intervals

Cool-down: 6 minutes

Total Time: ~50 minutes

Session 3 (Weekend): Zone 2 Endurance

Warm-up: 5 minutes

Main Set:

- 60-90 minutes at 60-75% FTP (140-174W)

- Include 2-3 x 5 min tempo efforts (85% FTP, ~197W) to build aerobic base

Cool-down: 5 minutes

Total Time: 60-80 minutes

Session 4: Sweet Spot

Warm-up: 10 minutes

Main Set:

- 3 x 10 minutes at 88-93% FTP (204-216W)

- 5 minutes recovery between intervals

Cool-down: 5 minutes

Total Time: 60 minutes