Do you really need lastused? Without replicating the "lastinv"-command it gets a lot easier.
German: Ich mein Du hast schon Mausrad und 1-3, wie oft wirst du dann mit q wechseln? Ohne das Ganze wirds etwas kürzer, ohne exec, zusätzliche cfgs und so weiter.

unbind "q"
unbind "KEY"
bind "KEY" "view"

alias viewoff "alias models "r_drawviewmodel 0"; alias view viewon"
alias viewon "alias models "r_drawviewmodel 1"; alias view viewoff"
viewoff

alias "s1" "slot1; models; bind MWHEELUP s3; bind MWHEELDOWN s2"
alias "s2" "slot2; models; bind MWHEELUP s1; bind MWHEELDOWN s3"
alias "s3" "slot3; r_drawviewmodel 1; bind MWHEELUP s2; bind MWHEELDOWN s1"

bind "1" "s1"
bind "2" "s2"
bind "3" "s3"

No, not at all.
Don´t quote a tl;dr and then complain about something not being mentioned. ;-)
Imho the roamer should be on the flank, unless he´s getting a buff atm or you planned a double soldier bomb for the next push.
Of course he needs a bit less heals, which is quite handy in team fights and on the midfight, but it´s not that much of a difference at all other points in time.

I haven´t said anything about 24/7 suiciding. Gunboats just give roamers the ability to bomb in and jump out or to bomb in places that are usually to far away because of the amount of jumps required.

If your scout(s) are playing a bit more passive, so you rarely need the shotgun as finisher, then you can equip gunboats for convenience (heals, more rjs). With gunboats you can jump in and out easier (i called this bombing, this is already considered pretty aggressive in europe) OR go for a suicide play on a medic far back. Considering that your scouts are playing rather passive, there´s no reason not to go for these plays.
Contrary if your scout(s) are playing aggressive you have to hold the flank and probably need the additional firepower of the shotgun, while you are a bit closer to your medic (depending on the map) so you can get heals/buffs easily, which negates the advantage of gunboats.

And of course, like #20 said, it´s depending on the map. Running gunboats all the time EXCEPT for the midfight (unless your roamer wants do to a shitload of jumps on the midfight) is a good idea for open maps (e.g. process) where the flank is miles away from the medic, so buffs wouldn´t last until the roamer is back on the flank (rjs/walking time) and the roamer would just waste time by going back to the medic. On smaller maps (e.g. gullywash) shotgun is superior most of the times. Although we like to suicide our roamer on the combo in gullywash midfights, if our demo does the rollout via choke, so the combo takes too much damage to stay in the fight or just gets killed. After that our roamer runs shotgun pretty much all the time.
This is just a rule of thumb, figuring out when exactly to run gunboats or shotgun is pretty hard, it depends on the map AND the team/the teams playstyle/your playstyle.

As a Euro i have to disagree with you. Basically some people wanted gunboats (aka funboats) and some were just whining "Why can´t we have unlocks?". Atm we´re playing the 6th Cup with Overdose, Gunboats, Boston Basher, Escape Plan and Paint Train allowed and no one complained about it so far plus most of the players in prem said they want these unlocks in season 14 or they´re at least fine with these unlocks being allowed. ->season 14 most likely with these unlocks

This has nothing to do with gunboats being the only choice for a roamer. Since my team plays both pcws with normal and with the 6th cup rules i can tell you that playing with a roamer who is using gunboats instead of the shotgun is neither better nor worse. It´s just requires a different playstyle. It doesn´t matter if it´s the midfight or anything else, if your roamer is running gunboats he will take a lot less heals, but he will also do a lot less damage and is basically limited to bombing in and getting key picks or distracting.

Just keep in mind that when the roamer is on gunboats you cannot rotate or switch pocket and roamer as effectively, that your teams damage output is a lot lower and that since your roamer should be going for key picks you´re pushing with only one soldier most of the time. If one of your scouts likes to do the "get in, get a pick, die"-thing then you probably want your roamer to play with shotgun to keep your teams damage output high enough to be able to capitalize on these picks.

tl;dr
shotgun for safe, passive style, less bombs, more positioning
guboats for bombing + key picks, 1 soldier down most of the time/during pushes