Sure, you can do that. However you have to realize there is no such thing as a software region unlocking for Blu-ray, so the custom firmware you're talking about will only affect DVD playback, not Blu-ray playback. Another issue is that you won't be able to use any (regular) firmware updates for the Panasonic, e.g. to enable playback of some "difficult" new blu-ray releases. Installing such an update would remove the custom firmware. If you're fine with that, go for it.

If you need Blu-ray zone unlocking as well, you need a hardware modification of either the Panasonic or the Oppo. For Oppo, easy-to-install kits can be ordered here.
Alternatively, you can order the player with the modification already built-in. E.g.
here (check out Available options / Modification below the specifications)
here and
here.

I'm not familiar with similar options for the Panasonic, but I reckon they must be out there.

BTW if you need to check whether a particular blu-ray release is zone coded or not, this is a good site (start by choosing either Region A or Region C at the top, depending on the locality of the release in question).

Good luck with your decision-making, Taro!     

P.S.
If you still need a year of saving, it is practically certain that by that time at least Panasonic will have updated its range of players. With Oppo you can't be sure - they will launch new products when they're ready for it (after extensive beta testing with a small group of trusted users), not according to a fixed schedule.

P.P.S.
You can get the Panny VT-30 for less than what you estimated for the GT-30 and 2 shutter glasses, e.g. here. It comes with 2 shutter glasses and a WiFi dongle included.

Hmmmm, I have never seen firmware that can change region coding for blu-ray before! From everything I've read until now I was led to believe this was technically impossible, and it HAD to be done through hardware modifications. So I hope the firmware you found delivers on what it promises to do!

With hardware modifications it's also necessary to press some buttons to manually change the region coding for blu-ray (for DVD this isn't necessary) - there is no "all regions" setting for blu-ray.

Good luck with your endeavour! And if there's anything in the future I can assist you with, just let me know. 

For myself, I found the simplest way was to buy a cheap unmodified player here, and import a cheap unmodified player from the states. No issues with chip modifications, and the risk of destroying your player by installing the chip.

And it has gotten easier. Amazon.com now ships Blu-Ray players to Belgium. I ordered a Samsung BD-D6500 a couple of weeks ago. Including expedited shipping and import tax it cost 170€. Ordered on monday, delivered on thursday 

Quoting Bad Father:

Quote:
Video yes, Audio no. PS3 will not pass-through HD audio when playing 3D Blu-ray discs. Audio will only be Digital 5.1 max.

This was only true for the first year or so. As of version 3.70, it supports DTS-HD Master Audio on 3D titles. You still would get lossy sound if you were watching a 3D movie with Dolby TrueHD, but there only a handful of those.