I'm in middle of opinion.
I'm AND versus the new engine idea, AND like new engine idea.

New engine, the game has lots of potential, but a new engine could make it much better, besides, it could help to laptops like mine, which lag with Blitz3D but runs good with Unity, so, new engine plz

In my opinion I'd vote for either Unity or an OpenGL engine that the developer may be comfortable with.

But mostly, I would let the developer decide what engine to use. It's his decision and his game after all.

I don't know much about engines, but from the info i gather, blitz seems to be pretty old, but like others have stated, i'd rather hear regalis opinion.

Hey, welcome back, haven't heard from you in a while.

Could definitely be a great decision for the game in the long run, and I agree with it, but it's mainly up to Regalis I'm afraid.
Whenever Regalis chooses to do this in the near future or not, eventually (I think) he'll have to replace the current engine with a better one.

Of course, it's his decision

I'd recommend Basic4GL. I remember it because it's the first programming language I ever learned to use.

Pros:
- It's free and open-source.
- It uses OpenGL to draw graphics on the screen.
- It's BASIC-based like Blitz3D, this should make it easier to learn and port the game.
- It has several plugins available, and they are available for free. These could help in enhancing the game.
- It might be more stable than Blitz3D.
- Most of the cons can be ignored.

Cons:
- The project is discontinued, it hasn't been updated since 2008.
- It's currently only available for Windows, and it's current state doesn't hint any chances of it being ported to another platform.
- I believe it doesn't have a built-in collision engine (this can be considered as a pro since we get more control over the game when the developer does things manually)
- It's unlikely find a plugin that will load b3d models, but... What do you think?

Edit: I do agree that it's Regalis' game and his decision is what will be done to the game. But he might need to find a better engine if he wants more people to be able to play.

Has anyone tried ogre3D?
http://www.ogre3d.org/gallery

A new engine sounds good to me. I do a good amount of game development, so trust me; switching engines is neither quick, nor fun. There WILL be problems no matter how talented the developers are and how good the new engine is. That being said, I suggest switching to Unity3D. I am aware that Unity does not have the same graphics potential as UDK, but anyone who has used both engines will tell you that what Unity lacks in power, it more than makes up for in usability. The program is quick and intuitive, and the community support is incredible. And while it may not be as powerful as UDK, it is still leaps and bounds ahead of Blitz, and many Indie games have been released with Unity to prove it (2 that come to mind are Surgeon Simulator 2013 and One Late Night).
Also, I mentioned this once before, but I did a little work towards recreating SCP: CB in Unity. Although this project still has a long way to go (it is a project I am making by myself and have had almost no time to devote to with school not being over yet), It has taught me a lot about Unity, as well as Javascript and C#, the two main scripting languages used with Unity. However, I doubt Regalis will want to switch unless the ported version already has most of the functionality of the original, so once school ends I may try to do some significant work on this port, and then see if Regalis will consider it.

I see this as a fantastic idea. The old engine, Blitz3D, simply will not do in the future. I followed the C++ conversion closely and I saw a late video of what the conversion would look like on the game. It looks amazing, and if this is what it looks like as the lesser C++ language, than I bet these other engines will make the game look fantastic.

Also, I understand that the conversion to an new engine will take a very long time. However, this will have to be necessary. A new engine will definitely fix the game up. For example, light. DYNAMIC light. Think of all the ideas that can be added. We can fix the light fixtures, add improved muzzle flash and even make some shadows. The possibilities are endless.

And please, don't make time your excuse for not wanting to convert. We have all the time in the world.

As for Regalis, well there is nothing to be done but to set yourselves some very good arguments and points.