My first router was made from MDF. Look for references to "JGRO" with Google - lots of people have built them. It may be OK in the warm dry areas of the USA, but in a British climate in an unheated garage it has the structural integrity and long-term stability of cold-rolled cow dung. I built that machine (and around 7 years ago, it probably cost no more than £500) before I found this forum and based on glowing reports from people who had built one. I also saw a similar machine built from ply at an exhibition at about that time, which persuaded me to have a go. And, yes, it did do the job I built it for (basically, house-sign style of engraved plaque) and it built a number of models for my son's architecture degree. It is now firewood. I went steel for the mk2. Not sure why you talk about it not being very "modifiable" - angle grinder with cutoff wheel and a MIG welder and away you go. I wrote it up on this forum (search for "AVOR") and if you look closely you can how crap the welding is. Grown men have cried when they've seen it. Do you know, though? It's a bloody marvellous machine that continues to please me every time I use it. Probably cost around £2500 all told. Prices don't go down that much as the machine gets smaller although these days I would source more from China which would cut costs a bit.

Hey, there's a whole range between toy and carved-from-concrete machines that some guys here build. I had a go at the first as well as something half-way through that range and I don't regret my early learnings. But I am glad that I had half an eye to the future and did buy a decent spindle, steppers and stepper drivers for the mk1 that could be reused. Even if that first machine bent under the weight of the spindle even before starting to cut!