God no, please.
To answer Tom - speed is a big part of athleticism. At least that seems to be the biggest correlation on which 1B maintain their production. Going through that list of 1B:
Pujols - one of the best players ever until age 30. Horrible waste of playing time and money after age 32
Bagwell lasted longer, but was also unusually athletic
Big Frank was amazing through age 29. He managed two good seasons after that.
Thome his his peak later and lasted a little longer. But he was much worse after age 33 than before it.
Cabrera started his decline at 31, played pretty well through 33, then fell off a bloody cliff.
Palmeiro lasted longer. But he was also athletic enough to be somewhat tolerable in the OF.
Freeman is a big outlier. But he's also very athletic for a 1B.
Votto fell off the cliff after 33
Goldschmidt is aging reasonably well, but is also sneaky fast.
Olerud is a an odd entry here - he's not a slugger at all. He still fell off a cliff after age 33.
Berkman became inconsistent after age 28, had his last great year at age 32, was pretty bad afterwards
Helton was great through age 30, had a couple of okay seasons at 31 and 33, but was otherwise bad
McGwire used steroids to stay strong through age 36. Is that still an option?
Mauer was pretty useless after age 30
Giambi was never the same after age 32, but had a bit of bounce for a couple years after putting up a 0.0 war year at age 33. He was negative WAR after that.
Teixeira is a really good comp for Alonso...and was already in decline at age 30 and was a horrible drag on his team after age 31
Delgado had a softer decline than most, but was still mostly a 2-win player after age 31
McGriff averaged about (eyeballing it here) 5+ war per year through age 30. He averaged about 2 war after. He hung around better than most, though.
Grace had a soft decline. But again, not a slugger.
Ryan Zimmerman basically fell apart after age 28.
The next guys on the list are Adrian Gonzalez, Rizzo, Derrek Lee, Edwin Encarnacion, and Mo freaking Vaughn.
Who on that list inspires hope in Alonso being productive on a five year contract that starts at age 30 (there's no chance he gets eight years on the market)?