I have not heard about the Nextcast lines, i do not know if they are known i Europe yet. what i am referring to are lines like this: (youtubelink)
https://www.youtube.com/watch?v=8Vt80CuXRmY
if this is truely a hybrid, i do not know, but it is interesting if it works with both scandi tips and light skagit tips (if it is possible?) personally, skagit are good for deep presentation, but for me as scandi caster and often use floating and intermediate tips, the skagit setup is not the optimal setup for me. but sometimes I need to get deeper, specially during and after a summer flood, then it could be useful to put on a heavier tip one my standard scandi set up. Well, anyhow an interesting discussion.
The line you posted above does seems from what they say in the video to have a similar taper (speaking in very broad terms of course) to what I posted above regarding the Winter Authority lines, if you read what I wrote about them. And I don't think those are the only two.
There is in actually no such thing as a "scandi tip" or a "skagit tip" in terms of the physics, only a tip that matches a line well. Likewise there may be other solutions to getting deeper to try first before switching to a different head, especially as you have a preference clearly stated for scandi tapers.
Dispensing for simplicity with the much more secondary issue of whether a tip has a bit of a taper or not, if a tip of a certain length and total weight (i.e. with a certain weight per unit LENGTH) casts well on your scandi head, for example a floating tip, then a denser (weight per unit VOLUME) tip with the same weight per unit length will sink better but cast exactly the same. I mention this because you said that you cast a floating and intermediate tip on your scandi lines OK, if I understood you. Going heavier in total weight, starting with the line, is usually, more or less, just for bigger flies. There are many other choices but the tips for this type of matching that I know best are the "Rio Replacement Tips". These are made in wt classes and given total lengths (10' or 15', but you can cut them) where each of the various sink rates, floating, intermediate, 3,6,8 ips all have the SAME total weight (therefore the same weight per unit length). So one thing you can try is just to match a denser (not heavier) tip to the scandi head you already have. Use the length and total weight, and then use the table for these tips to find the denser tips that match, and presto, you will be able to cast a faster sinking tip on your current scandi head!
To take a hypothetical example to make things clear - suppose a tip you use that casts well already with the flies you like to use is a 130gr floating tip that is 15' long. Then you could replace it by an 8ips (equivalent in sink rate to t11) 9w 15' rio replacement tip that weighs 129gr, or for that matter with a 3 or 6 ips 9w tip which all weigh the same. These should cast exactly the same, and turn over exactly the same as the floating tip that worked. No hinge effect, etc. Problem solved. There are other ways to make things work, but I have found this one particularly foolproof.
The overall moral without getting into many secondary details: its is the weight per unit length (linear density) of a line that determines how big a fly you can cast (as then which tips match the best), and the tips that match scandi heads will have less of that than skagit heads, and so be more limited. Also on a traditional nearly-level skagit head the tip matching will not matter as much. If you want to cast BIGGER flies, then you may eventually have to take a step toward the skagit taper heads with (at least) heavier butt sections, but up to a certain point skill can also compensate. If you just would like to get your current flies deeper then your problem can be solved to a large degree simply by matching the tips correctly as described above. Only if you can't cast the flies you want (or can't find a decently-matched sink tip) would you then be forced to change lines, though you might do so for many other reasons. But (to finally get back to the original post) in that case I think you are right, if you really like scandi heads the first step would be to take a baby step towards a line with a heavier butt instead of immediately jumping to a full-on skagit. Also as another valid option there are beautiful full intermediate scandi lines you could go to that will cast the same but get much deeper using the same tips. The line maker Steve Godshall was actually telling me recently that this is what the Europeans use a lot more often in such situations, but we in North America have not caught up yet.
Hope these ideas help somewhat. I know that trial and error are the traditional "non geek" way to figure this stuff out, but it can get expensive, especially if you are going to buy new heads.