I looked over the ideas and again, I would suggest a bit of caution and conservatism in this issue. As Janis said, Latvia restored the Satversme without replacing it like Estonia and Lithuania, so it's here to stay. And IMHO, Vaira sees her job as its protector, and any amending of it would definitely need her FULL support.
The more I look at the proposed ideas the more it's starting to look like the Lithuanian system. It seems that the root of the ideas come from a split mandates/PR system, the Lithuanian system is one of the simplest ways of doing it. Maybe the debate should be how different from the Lithuanian version would you want it to become?
The current Lithuanian system is 141 seats, with 70 seats by national PR and 71 electoral districts. The districts are done mostly by population, though that means Vilnius and Kaunas has tons of districts. However, it does account for some regional balance. Those are now done at first-past-the-post as they got rid of the run-off system. Originally there's been argument to use the Irish "second preference" system, but that was seen as too complex and indirect. So basically, it's done very much in the British system, though some candidates ended up winning with 17% of votes (with just over 50% turnout, that means only 8% or so of the district elected its rep). The British party system is more stable and usually you get a 2 or 3-way race (sometimes 4), but it rarely gets to a point where a candidate wins with under 20% of the votes. That's where there could be a weakness.
The 70 seats under PR is national, no districting. Any parties over 5% gets seats this way, no exceptions anymore. They have a strict formula so you don't end up with "extra" seats like in Germany. Coalitions need to have 7% to get seats. And it's national, so no regionalism at all in this. And now they have PR lists with people allow to list preferences, so some nonsimpatico folks could be crossed out.
So it's looking like what you are all proposing is closer to a modified Lithuanian system than a modified Latvian system. If the PR part is also done regionally, that would be a mess. Too difficult to deal with.
And also with the local electoral commissions, they have to be EVEN. You can't have the government/cabinet proposing half and President half, because then the political opposition would have no representation and would claim bias. It has to be even, with all major parties having some say. That gets messy, but still, you avoid the bias tag. And usually the left (SocDems) are opposition, and you don't want Bojars to play the same game as those SocDems in Albania did, causing the OSCE to call the elections UNFAIR and cause a civil war to break out. That is just too easy to happen for something so insignificant as not giving the opp some representation in the electoral commission.
If the group is bent on changing the system to add a personal dimension to the Saeima (away from full PR), then the Lithuanian model may work better. I am just worried that such a big tinkering of the system would be vigorously opposed by all sorts of parties and individuals with different agendas -- all wanting some form of status quo, either for personal gain or for sake of stability. Plus, some people may start bringing up the late 20s and early 30s on trying to change the parliamentary system.
Some of this also hinges on whether Vaira's re-elected or not in 2003. I doubt this could be done by then.
One key thing is that no matter how you change the electoral system at this stage, the problem remains in the political and party culture of the country. The British system works because it has party maturity. No parties outside the 3 main parties (Tories, Labour and LibDems) wins seats in England, and outside England only the national parties do (Plaid Cymru, SNP, and all the Ulster parties).
Latvia's political system is not so mature, and you'll get a bunch of radicals winning seats in the mandate system. Like in Lithuania, you end up with someone like Vytautas Sustauskas, a known anti-Semite and radical nut, being elected though is party didn't make it. I hate to see Latvia facing the same things, and in a society that is much more fragile in terms of ethnic relations than Lithuania, all it takes is one firebrand or two to be elected to make a total, total mess.
What if a Russian-minded (but Latvian citizen) ends up winning by a huge margin in Daugavpils, and riles people up more than the current set of Zhdanokas and Rubikses? What if some Perkonkrusts guy win a large margin in the countryside and becomes a nut like Gustavs Celmins and causes all sorts of ethnic strife? That is the danger of single constituencies, because you get the radical element.
That's just my two cents. I think the simpler the system, the better. But the change must be well-thought-out since it can't be changed again for a long time if the political culture is allowed to mature with system stability.
Hope all's well!