I took a look at your stats and I'm going to be blunt but please dont take offence. You are going down a similar route that a lot of people do after getting 99 in easy to achieve skills such as cooking, firemaking or fletching and start thinking that other 99s are equally as easy to achieve.
Are you fully aware of not only the cost in getting 99 smithing but also the time it takes to get it? A peek at the GE for the prices of gold and nature runes means it would cost you 68,233,339 gp to get to 99 con (you would also almost get 99 magic) assuming you use goldsmithing gauntlets. Whats the speed of superheats per hour?... somewhere around 2-2.5k superheats an hour? So it could take you around 80 hours of nonstop superheating... I think you might be underestimating how difficult that will be.
What would I do if I had your stats?... firstly I'd snag that last woodcutting level for 99 then I might try hunter. Now that the bots are gone the prices of chins has soared. From your level now to 99 you could sell those chins for 40m plus! Hunter is a fairly easy skill to level too. This will give you some money that you can use to spend on other skills. Focus perhaps on getting to 91 so that you can assist effigies in both construction and smithing.
But my last piece of advice is this...
Don't listen to me, or anyone else who tells you how to play! It's your game and play it the way YOU want to enjoy it
Edit:
I reread your post again and it specifically mentions construction. I recently purchased enough oak logs (at 21 gp each) to get to just before level 99 (I get 30k xp daily by assisting people so i have factored this in). I plan on starting stealing creation in a few weeks to get the 1,740 points I need.
My reccomendation to you is to go for the logs route and get your butler to send them to sawmill etc, it's a lot cheaper than just getting the planks ready cut from the grand exchange especially if youve done the quest which lowers the wages of the butler.
Just remember that as soon as you hit 91 con that you try to get the daily assistance exp from people in w117, this will save you a fortune. I would do enough stealing creation to get tge tools for 91 then get your con up to the level using up all your resources. Then I would go back to stealing creation remembering to get my assistance xp and then after a few days or weeks of stealing creation that "free" exp youve been getting will substantially lower the amount of points (tools) and logs that you need to get to 99. One week of giving assistance is 210,000 construction exp or 1750 less logs!