I am doubtful about this purchase putting a drain on Taiwan's procurement. The is no indication or proof that Taiwan is spending more than it can afford.
Taipei will eventually replace the existing tank fleet with a more modern design which will in all likelihood be smaller due to the increased capability and price tag it offers.
For a nation for with such a small landscape like Taiwan a thousand MBTs borders nearly on the verge of excessive. What they will get and how much will be dictated solely by their domestic needs and projections.
$1 billion (just for the tanks, with no support package) is about 8-10% of the defense budget. Since procurement is about 20-30% of the total budget, that's 50+% of the total defense procurement for one year going to one purchase (of very questionable operational utility) alone. $1 billion spread out over a several years, that essentially eats all of the ROCA's share of the defense budget (the ROC Army will probably get less than 33% since the ROCAF and ROCN have historically dominated procurement). That means the ROCA will have difficulty affording other things like artillery, anti-ship missiles, body armor, drones, helicopters, communications gear, cyber...
100 or so M1A2 at the start of the war would be whittled down to 20-30 tanks after a couple week of bombardment (assuming an 80% readiness rate). Now those 20-30 tanks have to engage a PLANMC force armed with every kind of ATGM, and dodge naval artillery, attack helicopters, fixed wing aviation, drones (including flocks of one way attack drones). And that's assuming their are no PLA MBTs in the neighborhood.
Two armored divisions would have around 600 tanks. That's expensive enough by itself, but then you need to procure modern IFVs and other such vehicles to keep up with the MBTs...
Two divisions (or their equivalent in brigade combat teams) would end up with north of 40,000 personnel. That's about 33% of the entire ROCA current end strength (which is only going to shrink in the future). In the future digital battlefield, that's a huge sunk cost