select objects by rectangle selection a la RTS

[integrality]

I actually do this by resizing an alpha channel object
I cant have it semi-transp (FPSKILLA) nor 0%alpha (It would hide things over it) so I'd like to stroke it with lines, possibly not with other 4 alpha channel objects as lines.

there are other standard possibilities for doing this in other ways?

[DanielRehn]

I usually use an active system box

[Surmulot]

I suppose an active overlay could work too (with transparency and a well-choosen color).