Yes, if you’re referring to the Wednesday workout. I recommend MV for you. Just do what you can but make sure to get the interval sessions in.
This leads me to believe your FTP is a little low. If you’ve been a long time user and if you’re sufficiently being challenged (FTP is accurate), I’d expect you to have an off day or challenging workout that requires an intensity reduction and/or some back peddling at some point.
Yes, up FTP 2-5% or increase workout intensity 2-5%. Do MV and substitute non interval days for outdoors as you like. If life is too busy, don’t worry if you have to miss the occasional workout. That being said, SSB2 is significantly more challenging than SSB1, so tread lightly jumping to MV from LV and increasing FTP/intensity. You may need to start with MV and see how that goes first. If not being challenged enough, bump intensity/FTP a bit.
I’d stick with the Base-Build-Specialty progression. Remember, you will be building muscle endurance during Base that may not show up in FTP gains.
Lastly, if you use TR up until warm weather, then ONLY do outdoor rides, your fitness and FTP will likely decline. Unless you are very disciplined and continue structure and intervals outside, any gains through TR will slowly slip away. So when you start back up with TR when it’s cold again, you’ll be starting from square one, expecially since you’re a casual summer rider.
I recommend that once it gets warm, continue at a minimum, two structured indoor interval rides (maybe Tuesday and Thursday) and do the rest outdoors. Maybe go back to LV at this point. This will ensure consistent growth towards higher fitness. Then as you enter Cross season, do a Build than Specialty. The Specialty phase is not necessary meant for raising fitness (FTP) but rather refining specific demands (icing on the cake). So without a Base and Build in succession, the Specialty is not doing you much good.
Ideally you’d set up you calendar to go through a complete Base-Build-Specialty where the Specialty phase ends mid/late race season. Then you’d hold onto that “peak” the remainder of race season. As the weather changes during your training year, you’d do outdoor rides but keep structure and continue working towards you race goals.