I went the opposite a few times. Parents always paid for trips so we stayed at the Poly, GF and BC. Then I went and did a split so I could afford it on my own.
As far as transportation, you still need a bus for all the resorts to get to at least 2 parks (unless you are staying at an Epcot resort and walk then the IG to the monorail station to get to the MK but I wouldn’t do that). But on the flip side, MK and Epcot are my favorite parks so I stay at the Poly so we avoid the bus as much as possible and just go to those parks most days. I do love the boat to/from the MK though, less people on it and so peaceful!
Pool-kids love the pool no matter what. My kids couldn’t always do the water slide and were content with swimming in the quiet pool or the themed pool minus the slide. The last time we went in 2013, they all could swim so we sat in a spot where we could see them in the entire pool and they were free to go (youngest was 7). But they spent the entire afternoon playing pool games, they loved it! We only did the pool on non park days so the rest breaks were just that, a nap!
So since I didn’t make the switch, what I did not like about the mod/value was the lack of light-I like natural light so to open the slider curtain is a bonus. I felt like I had to have the curtain closed in the mod/value because everyone could see in as the walkway was right there. Other then that I had no issues with staying there. So I think going from the boardwalk to pop would be fine.
And as above, park proximity is the deal breaker. We mainly go to MK and Epcot so the Poly is our choice. This year I have convince my husband to do a split stay so we will have 5 nights at the BC followed by 5 at the Poly. I have not stayed at the BC since the summer of 1990. He just told me 2 days ago he isn’t sure he is going to like it but i know he will love the boat to the studios.