- If you where going to play in a "real" metagame, what would you cut for a Meddling Madge? I myself think a Brainstorm could be cut because it, like the Madge, usually doesn't get played on turn 1, so the extra casting cost won't matter, and because Brainstorm usually searches for disruption while Madge is disruption itself.
You could cut a Brainstorm, but I am a huge supporter of the full playset in the deck. It is never a bad topdeck, and gets you cards you want now in some cases. God its a hard decision on what to cut, the creature base probably shouldn't be altered except for adding the Mage, and the other spells need to be 4-ofs as well since you want to see them first turn (Vial/Chalice). The card that I probably felt didn't pull its weight enough was Ninja, but that was only because I saw heaps of creatures all day. Against any "normal" deck it would be ownage card advantage, so it should stay as 3. Now that I look at my list, I guess it would almost have to be the Brainsorm that you would cut, since everything else is almost essential (unless you want to cut the whole Tutor/Tinker/Colossus package). I guess my answer is it's your choice

- Would you advise playing the Tinker > Darksteel Colossus combo in a budget deck? Did you ever Mystical Tutor for something else besides Tinker (Ancestral Recall of Time Walk)?
I'll answer this question based on how I am interpreting it, and that is if there are still enough artifact sources to make Tinker worth it. With the loss of only 2 Moxen and the Lotus, you still have 4 Chalice and 4 Vial, and even your Factories can turn into artifacts to sac. I guess making it a budget deck would mean that Tinker is the only target for your Mystical Tutor, which could cause some issues. If you are in a budget metagame, it will lose some potency since you will most likely cut Chalice, but in that type of meta Colossus should be even more powerful. Personally I did tutor up a Time Walk once, when one more attack phase would wipe my opponent out completely. I tried to get too cute one game I should have won when I Tinkered into a Colossus, which met Gilded Drake and I promptly lost a game I shouldn't have. Tutoring a Recall is never a bad move either, so you have 3 potential game-breaking targets for the Tutor and you just have to decide which one is best in the situation.
- How good was Black Lotus? This may seems strange, but in some of my games I got the Lotus in my opening hand, but was wishing it was a land instead. Plus, the Lotus gives Goblin Welder a way to fuck with your Chalice and Jitter which happend a few times in testing.
Black Lotus in this deck offers the same first turn insanity it does in other decks. I think I only drew it once or twice, but the fact that you can play something like a first turn Mongrel and Jitte, then equip it next turn almost means that's good game unless they have creature removal. It can also randomly bring about first turn Tinker if you are playing it. About the Welder issue, if you have an active Jitte in play the Welder isn't even a problem, and if you play a Jitte into his Welder then its kind of stupid unless you want your Lotus back or something

. The fact is you have one card in your deck that makes Welder mess with your artifacts, so chances are you won't even get in the situation. Also, if you have a Chalice in play already it should have slowed them down enough to get yourself some board position, or you have played it too late and it was useless anyway so they can go ahead and weld it out for your Lotus. On the whole, the advantages of Black Lotus FAR outweigh the disadvantages of a "potential" situation with a Welder in play.