Would this tend to politicize the court? As it is, the court can at least ostensibly maintain some distance from the political lawmaking process. If it was an integral part, judges would be subject to a lot more political pressure.
As it stands, the court is the arbiter for whether a law (or section of a law) is legitimate and how it's applied. All this would do is remove the latency between legislation being written and it being 'tested'.
It probably wouldn't be practical, given that they currently don't review anywhere near 100% of legislation (but maybe that is a feature).
I would be concerned about the situation where the court effectively ends up with a veto and maybe decides that they should be the ones in charge. The only way out of that pickle is to reject the constitution.
I don't see how pressure can be applied to a position with a lifetime appointment. You could say, perhaps, that the powers that be could try to extract some pledge of allegiance before nominating/confirming a new justice, but what's to stop the justice from immediately reneging on a clearly unethical / unenforceable agreement?
Edit: I think the argument could be made that it weakens the checks and balances though. As it stands the court can overrule lawmakers, but it takes a long time generally for laws to wind up there. If they have a more immediate veto power who checks them? Not the lower courts which, to some extent, acts as a filter today.
> "I don't see how pressure can be applied to a position with a lifetime appointment."
People don't have to be forced to do things to make effectively political decisions. Being incentivized also works. And social incentive seems to work at least as well as monetary incentive.
People have families and lives and friends.
Consider that the "broccoli" argument against the PPACA's personal mandate -- an argument broadly laughed off by constitutional scholars -- was echoed verbatim by justices with mere social connections to the groups who originally espoused said laughable argument.
