I'm pretty sure that all employer backed retirement plans (ie 401k's) require paycheck contributions, or else they become IRAs and you play by that set of rules.
You can reallocate your TSP funds as many times as you like however you like through TSP's website. No DD-ID10T form necessary, and unlike Vanguard they don't have a minimum holding time before you can trade again. But yes, you do have to purchase one of their funds. They do lack specificity (you essentially get to choose one of 5 index funds), but they also have dirt cheap fees.
Most servicemembers would make more money for retirement with the blended plan than not, and servicemembers who leave before 20 years get to keep a little something. Again, this is a pretty good system, the problem is that they want to raid Tricare to pay for it.
I had an employer plan (working for a state university) that gave us a 10% 403b contribution, no match required. So basically it was an extra 10% pay, dumped into a retirement account. Beyond that, we were able to contribute more, but there was no match. Unusual, but not unheard of.
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I didn't read this article in the OP, but last I read about this plan, it was basically FERS. And FERS offers a 1% contribution with no match required. After that, the employee has to pony up to get the match. So it seems this plan does have a something for nothing. Which is good as I wonder how many E-3s can/will afford to give up some of their pay to get a match. At least they'll still have that "free" 1%.
That said, being that Husband plans to do 20 and is most of the way there, I'm glad he'll be grandfathered in. Certainly this new plan is a big loss for those who do 20. The 20% reduction in benefit amount (from 50% of pay to 40% of pay) isn't catastrophically different, especially with the TSP contribution and match, and that small bonus at 12 to make up for some of it. But waiting until retirement age to start the pension is a giant difference. That makes me wonder what this will do to retention, when the carrot on the end of the stick is much smaller and they've added a lot of interim carrots for those not interested in the larger one at the end. And how much will be spent on bonuses to counteract any possible retention repercussions?
Is retirement a retention program, or a fairness program?
In the end, the changes aren't truly for the purpose of making things more fair (something for everyone, not just the 20s!), though that's how it's being sold. It's a financial decision. This should be be cheaper, assuming they don't have to use a ton of bonuses to keep people in or go to the model of adding more guys at the beginning (and paying their salary and training) so that you end up with the numbers you need at O-4+.
Since it's a volunteer service, I guess the labor market will be the final arbiter on whether this is works for enough people, and in the right ways, to give the military the manning it needs.